Apparatus and method for performing random access in beam-formed system

ABSTRACT

A method for performing a random access is provided. The method includes identifying a first downlink (DL) reception (RX) beam based on a measurement on a beam measurement signal, identifying a first uplink (UL) transmission (TX) beam corresponding to the identified first DL RX beam and transmitting at least one random access preamble for an RX sweeping at a base station, using the identified first UL TX beam based on a first power.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/276,030, filed on Feb. 14, 2019; which is a continuationapplication of prior application Ser. No. 15/443,562, filed on Feb. 27,2017, which has issued as U.S. Pat. No. 10,278,160 on Apr. 30, 2019 andwas based on and claimed priority under 35 U.S.C. § 119(e) of a U.S.Provisional patent application filed on Feb. 26, 2016 in the U.S. Patentand Trademark Office and assigned Ser. No. 62/300,333, and of a U.S.Provisional patent application filed on May 11, 2016 in the U.S. Patentand Trademark Office and assigned Ser. No. 62/334,660, the disclosure ofeach of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to wireless communication technologies.More particularly, the present disclosure relates to a filter bankmulticarrier (FBMC) modulation-based signal transmitting method, signalreceiving method and device.

BACKGROUND

To meet the demand for wireless data traffic having increased sincedeployment of 4th-generation (4G) communication systems, efforts havebeen made to develop an improved 5th-generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post long term evolution(LTE) System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), full dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, hybrid frequency shift keying (FSK) andquadrature amplitude modulation (QAM) modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies, suchas a sensor network, MTC, and M2M communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RAN as theabove-described big data processing technology may also be considered tobe as an example of convergence between the 5G technology and the IoTtechnology.

In the recent years, several broadband wireless technologies have beendeveloped to meet the growing number of broadband subscribers and toprovide more and better applications and services. The second generationwireless communication system has been developed to provide voiceservices while ensuring the mobility of users. Third generation wirelesscommunication system supports not only the voice service but also dataservice. In recent years, the fourth wireless communication system hasbeen developed to provide high-speed data service. However, currently,the fourth generation wireless communication system suffers from lack ofresources to meet the growing demand for high speed data services.

A method of providing a generally high data transmission rate includes amethod of providing communication using a wider frequency band and amethod of increasing frequency usage efficiency. However, it is verydifficult to provide a higher average data rate through the lattermethod. This is because communication technologies of a currentgeneration provide frequency usage efficiency close to a theoreticallimit and thus, it is very difficult to increase the frequency usageefficiency up to that or more through a technical improvement.Accordingly, it can be said that a feasible method for increasing thedata transmission rate is a method of providing data services throughthe wider frequency band. At this time, the thing to consider is anavailable frequency band. In view of the current frequency distributionpolicy, a band in which a broadband communication of 1 GHz or more ispossible is limited and a practically selectable frequency band is onlythe millimeter wave band of 30 GHz or more. Such a signal of the highfrequency band causes severe signal attenuation according to a distancedifferently from a signal of a frequency band of 2 GHz used by thecellular systems of the related art. Due to such signal attenuation,service providing coverage of a base station using the same power as thecellular systems of the related art will be considerably reduced. Inorder to solve this problem, a beam forming technique is widely usedwhich concentrates transmission/reception power into a narrow space toincrease transmission/reception efficiency of an antenna.

Due to high path loss, heavy shadowing and rain attenuation reliabletransmission at higher frequencies is one of the key issues that need tobe overcome in order to make the millimeter wave systems a practicalreality. The lower frequencies in cellular band having robust linkcharacteristics can be utilized together with higher frequencies inmmWave band to overcome the reliability issues.

FIG. 1 illustrates a deployment of a wireless communication system usinghigher frequencies according to the related art.

Referring to FIG. 1, high frequency small cells are deployed in coverageof low frequency (LF) macro cell. Mobile station (MS) first connectswith LF base station (BS)/eNB (master BS/eNB). LF BS/ENB adds highfrequency (HF) BS (secondary BS) to meet quality of service (QoS)requirements high data rate (HDR). A user equipment (UE) communicateswith both master BS/eNB and Secondary BS/eNB.

A typical procedure of adding a secondary BS in prior art is shown inFIG. 2 according to the related art.

FIG. 2 is a signal flow diagram illustrating a typical procedure ofadding a secondary base station according to the related art.

Referring to FIG. 2, a master eNB (MeNB) decides to add a secondary eNB(SeNB) based on measurement result from the UE and sends additionrequest to the SeNB. The SeNB performs admission control and sendsacknowledgement with the SeNB radio resource configuration. The MeNBsends the RRCConnectionReconfiguration message to the UE including thenew radio resource configuration of the SeNB according to theSCG-Config. The UE applies the new configuration and replies withRRCConnectionReconfigurationComplete message. The MeNB informs the SeNBthat the UE has completed the reconfiguration procedure successfully.The UE performs Uplink synchronisation towards the SeNB using the randomaccess procedure. After the random access procedure, the UE may starttransmitting and receiving the data from the SeNB.

In a beamformed system, the control plane operation is performed in abeam formed manner. In such a system, sending of the random accesspreamble (RACH) and the random access response (RAR) is also performedin a beam formed manner. However since at the time of random accessprocedure the best beams on which to operate are not known, theprocedure typically involves sending the same information on multiplebeams and attempted to be received by the receiver using all its receivebeams. After this procedure, the best beams for transmission andreception are known at both the receiver and the transmitter. Howeverthis procedure is time consuming since it involves sending and receivingsame information over multiple beams. Since future systems are requiredto achieve ultra-low latency and since random access is a typicalprocess for establishment of data transfer, it is of utmost importanceto optimize it to the maximum.

Therefore, a need exists for an enhanced random access procedureconsidering the beam forming.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method for performing a random access by anapparatus in wireless communication system.

In accordance with an aspect of the present disclosure, a method forperforming a random access by an apparatus in wireless communicationsystem is provided. The method includes identifying a first downlink(DL) reception (RX) beam based on a measurement on a beam measurementsignal, identifying a first uplink (UL) transmission (TX) beamcorresponding to the identified first DL RX beam and transmitting atleast one random access preamble for an RX sweeping at a base station,using the identified first UL TX beam based on a first power.

In accordance with another aspect of the present disclosure, anapparatus in wireless communication system is provided. The apparatusincludes a transceiver configured to transmit and receive signals, andat least one processor configured to identify a first DL RX beam basedon a measurement on a beam measurement signal, identify a first UL TXbeam corresponding to the identified first DL RX beam, and transmit atleast one random access preamble for an RX sweeping at a base station,using the identified first UL TX beam based on a first power.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a deployment of a wireless communication system usinghigher frequencies according to the related art;

FIG. 2 is a signal flow diagram illustrating a typical procedure ofadding a secondary base station according to the related art;

FIG. 3 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure;

FIG. 4 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure;

FIG. 5 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure;

FIG. 6 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure;

FIG. 7 is a schematic diagram illustrating transmission of a randomaccess preamble according to an embodiment of the present disclosure;

FIG. 8 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure;

FIGS. 9A and 9B are signal flow diagrams illustrating a method for abeamformed random access procedure according to an embodiment of thepresent disclosure;

FIG. 10 is a schematic diagram illustrating transmission of a randomaccess preamble according to an embodiment of the present disclosure;

FIGS. 11A and 11B are signal flow diagrams illustrating a method for abeamformed random access procedure according to an embodiment of thepresent disclosure;

FIGS. 12A and 12B are signal flow diagrams illustrating a random accessprocedure based on channel reciprocity according to an embodiment of thepresent disclosure;

FIGS. 13A and 13B are signal flow diagrams illustrating a problem whenrandom access procedures are performed by multiple user equipment (UEs)with one base station according to an embodiment of the presentdisclosure;

FIGS. 14A and 14B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct randomaccess response (RAR) according to an embodiment of the presentdisclosure;

FIGS. 15A and 15B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure;

FIGS. 16A and 16B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure;

FIG. 17 is a schematic diagram illustrating identification of a RARaccording to an embodiment of the present disclosure;

FIGS. 18A and 18B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure;

FIGS. 19A and 19B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure;

FIGS. 20A and 20B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure;

FIG. 21 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIG. 22 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure;

FIG. 23 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIG. 24 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure;

FIG. 25 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure;

FIG. 26 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIG. 27 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure;

FIGS. 28A and 28B are flowcharts illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIG. 29 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIGS. 30A and 30B are flowcharts illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIGS. 31A and 31B are flowcharts illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure;

FIG. 32 is a flowchart illustrating a method for a random accessprocedure in a new radio access technology (RAT) according to anembodiment of the present disclosure;

FIG. 33 is a flowchart illustrating a method for a random accessprocedure in the new RAT according to an embodiment of the presentdisclosure;

FIG. 34 is a flowchart illustrating a method for a random accessprocedure in the new RAT according to an embodiment of the presentdisclosure;

FIG. 35 is a flowchart illustrating a method for a random accessprocedure in the new RAT according to an embodiment of the presentdisclosure;

FIG. 36 is a block diagram of a terminal apparatus according to anembodiment of the present disclosure; and

FIG. 37 is a block diagram of a base station (e.g., a master eNB (MeNB)or a secondary eNB (SeNB)) according to an embodiment of the presentdisclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

FIGS. 1 to 8, 9A and 9B, 10, 11A and 11B, 12A and 12B, 13A and 13B, 14Aand 14B, 15A and 15B, 16A and 16B, 17, 18A and 18B, 19A and 19B, 20A and20B, 21 to 27, 28A and 28B, 29, 30A and 30B, 31A and 31B, 32 to 35,discussed below, and the various embodiments used to describe theprinciples of the present disclosure in this patent document are by wayof illustration only and should not be construed in any way to limit thescope of the disclosure. Those skilled in the art will understand thatthe principles of the present disclosure may be implemented in anysuitably arranged telecommunication technologies.

To make objectives, technical solutions and advantages of the presentdisclosure more clear, detailed descriptions about the presentdisclosure will be provided in the following, accompanying with attachedfigures and embodiments.

In a plurality of the embodiment of the present disclosure, a BeamformedRandom Access Procedure for next generation communication System isprovided.

A system under consideration is next generation communications systemwherein a base station employing a carrier frequency at higherfrequencies (commonly referred to as high frequency (HF)-base station(BS)) than the sub-3 GHz typical cellular frequency is used for nextgeneration communication (commonly referred to as 5th-generation (5G))while another base station employing lower carrier frequency (commonlyreferred to as low frequency (LF)-BS) consisting of legacy cellular band(sub-3 GHz) is used for supporting communications on the HF-BS. TheHF-BS is used typically for providing high data communications whileLF-BS is used for legacy operations like lower data rates, supportinghigh mobility users, supporting control plane signaling, and the like.More particularly, a single procedure may be achieved by the joint usageof both the HF-BS and the LF-BS.

In this description, the procedure of random access is described in thelight of such a HF-BS and LF-BS system which is more commonly referredto as 4th-generation (4G)+5G system or a Non-Standalone 5G System sincethe 5G (HF-BS) operates in conjunction with a LF-BS (5G). In such asystem, one possible deployment scenario can be where the LF-BS'coverage overlaps with the coverage of one or more HF-BS' coverage. Sucha deployment is further illustrated in FIG. 1. Further in the context ofthis disclosure, it is assumed that the mobile station (MS) capable ofoperating on both the HF-BS and LF-BS first connects with the LF-BS(which is also synonymously referred to as master BS-MeNB) and then theLF-BS adds the HF-BS (which is also synonymously referred to assecondary BS-SeNB) to the set of BSs used to serve the MS in order tomeet the desired quality of service (QoS) requirement of the trafficflows established by the MS. Further in the context of this disclosureit is considered that the MS performs Idle mode operations (for e.g.,cell reselection, monitoring paging, listening to system information,and the like) only on the LF-BS.

The procedure of random access described in this description is alsoapplicable for a system in which MS first connects with the HF-BS andthen the HF-BS adds the other HF-BS.

The procedure of random access described in this description is alsoapplicable for a system in which the MS first connects with the HF-BSand then it is handed over to another HF-BS (which is also synonymouslyreferred to as target eNB). In this case the MeNB in the description isa source eNB and the SeNB in the description is a target eNB. Further inthe context of this disclosure for the purpose of illustration, it isassumed that HF-BS operates in the millimeter wave carrier frequencyrange wherein beamforming is essentially used for achieving realistictransmission range of communication. However the concept holds good forany range of frequency if beamforming is used in the downlink (DL) anduplink (UL).

Method 1:

This method of the disclosure is illustrated in FIG. 3 according to anembodiment of the present disclosure.

FIG. 3 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure.

Referring to FIG. 3, at operation 311, the user equipment (UE)beamforming capability is send by the MeNB 302 to the SeNB 303 forexample in the SeNB Addition Request wherein the said capabilityincludes the Number of TX Beams (N) and the Number of RX Beams (Q)supported by the UE. At operation 312, the SeNB 303 transmits the SeNBAddition Request ACK including its beamforming capability for example inthe HF random access preamble (RACH) Config (or in any other systeminformation) wherein the said capability includes the Number of TX Beams(P) and the Number of RX Beams (M) supported by the SeNB. Instead ofindicating number of RX beams supported by the SeNB 303, the SeNB 303may indicate the number of times (M) the UE 301 needs to repeat thephysical random access channel (PRACH) transmission from each TX beam.The parameter M is greater than or equal to one. At operation 313, theMeNB 302 transmits the radio resource control (RRC) ConnectionReconfiguration including the received HF RACH Config to the UE 301.According to various examples, the HF RACH Config may be broadcasted bythe MeNB 302, or the HF RACH Config is divided in two parts: HF RACHConfig Common and HF RACH Config Dedicated. The Common information isbroadcasted by the MeNB 302, and the dedicated information is sent indedicated signaling from the SeNB 303 to the UE 301 via the MeNB 302.

At operation 314, the UE 301 transmits the RRC ConnectionReconfiguration Complete to the MeNB 302, and at operation 315, the MeNB302 transmits the SeNB Reconfiguration Complete to the SeNB 303.

At operation 316, the RACH Preamble is transmitted from the UE 301 tothe SeNB 303. At operation 316 a, the UE 301 transmits the RACH Preambleusing N TX Beams wherein transmission on each TX Beam is repeated Mtimes sequentially. RACH preamble selected for transmission can be samefor all N TX beams. Alternately, RACH preamble is randomly selected foreach TX beam transmission. In an embodiment of the present disclosure,the UE 301 may wait for random access response (RAR) after transmittingPRACH using a TX beam M times. If the RAR is not received, the UE 301transmits PRACH using next TX beam M times and then waits for the RARand so on. In another embodiment of the present disclosure, the UE 301may wait for the RAR after transmitting PRACH using multiple TX beamswherein transmission from each TX beam is repeated M times. If the RARis not received, the UE 301 transmits PRACH using next set of TX beams Mtimes and then waits for the RAR and so on. At operation 316 b, the SeNB303 receives the RACH Preamble transmitted by using M RX Beams.

At operation 317, the RAR is then transmitted from the SeNB 303 to theUE 301. At operation 317 a, the SeNB 303 transmits the RAR using P TXBeams wherein each TX Beam is repeated Q times where Q is the Number ofRX Beams at UE. At operation 317 b, the UE 301 receives the RAR using QRX Beams sequentially. The starting slot (e.g., subframe or TTI) orslots for the RACH Preamble transmissions and the corresponding RARreceptions can be indicated in the HF RACH Config. PRACH resource(s) andPRACH sequence(s) used by the UE is also indicated in HF RACH Config. HFRACH Config may indicate which PRACH resources/PRACH sequences to beused for each PRACH beam formed transmission. In an embodiment of thepresent disclosure, messages between the UE 301 and the SeNB 303 can betransparently transmitted by the MeNB 302. The information about thesystem frame number can also be included in the RAR. System frame numberis the radio frame number of the radio frame in which the RAR istransmitted/received by SeNB/UE. This information can be used by the UE301 to synchronize with system frame number timing of the SeNB 303. TheUE 301 is not required to read the physical broadcast channel (whichcarries master information block) of the SeNB 303.

Method 2:

This method of the disclosure is illustrated in FIG. 4 according to anembodiment of the present disclosure.

FIG. 4 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure.

Referring to FIG. 4, at operation 411, the UE beamforming capability issend to the SeNB 403 for example in the SeNB Addition Request whereinthe said capability includes the Number of TX Beams (N) and the Numberof RX Beams (Q) supported by the UE. At operation 412, the SeNB 403transmits the SeNB Addition Request ACK including its beamformingcapability to the UE 401 for example in the HF RACH Config (or in anyother system information) wherein the said capability includes theNumber of TX Beams (P) and the Number of RX Beams (M) supported by theSeNB. Instead of indicating number of RX beams supported by the SeNB403, RACH config may indicate the number of times (M) the UE 401 needsto repeat the transmission from each TX beam. The parameter M can begreater than or equal to one.

At operation 413, the MeNB 402 transmits the RRC ConnectionReconfiguration including the received HF RACH Config to the UE 401.According to various examples, the HF RACH Config may be broadcasted bythe MeNB 402, or the HF RACH Config is divided in two parts: HF RACHConfig Common and HF RACH Config Dedicated. The Common information isbroadcasted by the MeNB 402, and the Dedicated information is sent indedicated signaling from the SeNB 403 to the UE 401 via the MeNB 402. Atoperation 414, the UE 401 identifies the ‘Best DL TX Beam’ using theDownlink synchronization signals or reference signals transmitted by theSeNB 403. At operation 415, the UE 401 then reports the identified ‘BestDL TX Beam ID’ by including it in the RRC Connection ReconfigurationComplete. In alternate embodiment wherein Downlink synchronizationsignals or reference signals are transmitted using multiplesynchronization signal (SS) blocks, SS block ID of SS block in which theUE 401 has received the synchronization signal or reference signal withbest signal quality is reported instead of DL TX beam ID. At operation416, the MeNB 402 then transmits the received ‘Best DL TX Beam ID’ or SSblock ID by including it in the SeNB Reconfiguration Complete.

At operation 417, the RACH Preamble is transmitted from the UE 401 tothe SeNB 403. At operation 417 a, the UE 401 transmits the RACH Preambleusing N TX Beams wherein transmission on each TX Beam is repeated Mtimes. RACH preamble selected for transmission can be same for all N TXbeams. Alternately, RACH preamble is randomly selected for each TX beamtransmission. In an embodiment of the present disclosure, the UE 301 maywait for the RAR after transmitting PRACH using a TX beam M times. Ifthe RAR is not received, the UE 301 transmits PRACH using next TX beam Mtimes and then waits for the RAR and so on. In another embodiment of thepresent disclosure, the UE 301 may wait for the RAR after transmittingPRACH using multiple TX beams wherein transmission from each TX beam isrepeated M times. If the RAR is not received, the UE 301 transmits PRACHusing next set of TX beams M times and then waits for the RAR and so on.At operation 417 b, the SeNB receives the RACH Preamble using M RXBeams. The starting slot (e.g., subframe or TTI) for the transmission ofthe RACH Preamble can be indicated in the mmW RACH Config. The ‘Best DLTX Beam ID’ or SS block ID may be indicated in the RACH Preambleoptionally by selecting the PRACH preamble and/or PRACH resourcesaccording to DL TX Beam ID or SS block ID. There is mapping betweenPRACH preamble and/or PRACH resources and DL TX Beam ID or SS block ID.This mapping can be signaled in RACH config.

At operation 418, the RAR is then transmitted from the SeNB 403 to theUE 401. At operation 418 a, the SeNB then transmits the RAR using theBest DL TX Beam as reported (in PRACH transmission (operation 417) or inRRC Connection Reconfiguration complete (operation 415)) by the UE 401.In an embodiment in which SS block ID is reported by the UE 401, theSeNB 403 transmits the RAR using the DL TX Beam which is used by the eNBfor transmitting the synchronization signal or reference signal in theSS block corresponding to SS block ID. The slot of transmission of theRAR can be indicated in the HF RACH Config or alternatively, the RAR istransmitted at a slot derived from the slot on which RACH Preamble isreceived. At operation 418 b, the UE 401 accordingly monitors theindicated the RAR slot or it monitors the RAR slot according to thepre-specified mapping between RACH Preamble slots to the RAR slot. Thetiming advance (TA) and system frame number (SFN) information may alsobe included in the RAR. In an embodiment of the present disclosure,messages between the UE 401 and the SeNB 403 can be transparentlytransmitted by the MeNB 402. The information about the system framenumber can be included in the RAR. System frame number is the radioframe number of the radio frame in which the RAR is transmitted/receivedby SeNB/UE. This information can be used by the UE 401 to synchronizewith system frame number timing of the SeNB 403. The UE 401 is notrequired to read the physical broadcast channel (which carries masterinformation block) of the SeNB 403.

According to alternative embodiments of the present disclosure, the RARcan be transmitted in slots using the best DL TX beam. The UE 401receives the RAR using all RX beams. The best DL RX beam ID can also beindicated to the SeNB 403 together with the best DL TX beam ID. Thispair can be used to identify slot for the RAR transmission.

In method 1 and 2, the HF RACH configuration may further includes atleast one of Dedicated Preamble Configuration: Preamble Sequence,Preamble Valid Duration, Beam formed RACH Slot Configuration,frame/subframe/slot, and the like, for RACH transmission, the SeNBbeamforming capability, Number of TX beams, Number of RX beams, TX/RXbeamforming gain, Timing offset between frame/subframe of the MeNB andslot of the SeNB, and Number of Best DL TX/RX beam to report.

In method 1 and 2, the HF RACH configuration may also include Number ofTX beams to transmit (N) which is Less than equal to number of TX beamssupported by the UE and Number of times each TX beam is repeatedconsecutively (M) for the PRACH transmission, and number of TX beams totransmit (N) which is Less than equal to number of TX beams supported bythe eNB and Number of times each TX beam is repeated consecutively (M)for the RAR transmission.

Method 3:

Embodiment 1 (Beam Feedback)

This Method of the disclosure is illustrated in FIG. 5 according to anembodiment of the present disclosure.

FIG. 5 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure.

Referring to FIG. 5, at operation 511, an MeNB 502 transmits the SeNBAddition Request. At operation 512, an SeNB 503 transmits the SeNBAddition Request ACK including the HF RACH Config. At operation 513, theMeNB 502 transmits the RRC Connection Reconfiguration including thereceived HF RACH Config to a UE 501. According to various examples, theHF RACH Config may be broadcasted by the MeNB 502, or the HF RACH Configis divided in two parts: HF RACH Config Common and HF RACH ConfigDedicated. The Common information is broadcasted by the MeNB 502, andthe dedicated information is sent in dedicated signaling from the SeNB503 to the UE 501 via the MeNB 502.

At operation 514, the UE 501 identifies the ‘Best DL TX Beam’ andcorresponding ‘Best RX beam’ by measuring the HF cell. For example, ifthe UE 501 is doing RX beamforming then it uses all the RX beams one ata time to check the best received strength for a particular TX beam andthis procedure is then repeated for all TX beams. After completion ofall the RX-TX beam pair measurements, the UE 501 picks the one with thebest received signal strength.

At operation 515, the UE 501 reports the ‘Best DL TX Beam ID’. The UE501 can report the ‘Best DL TX Beam ID’ in the ‘RRC ConnectionReconfiguration Complete’ message that it sends to the MeNB 502 inresponse to the reception of RRC Connection Reconfiguration sent by theMeNB 502 for the addition of the HF cell to the UE 501. In alternateembodiment wherein Downlink synchronization signals or reference signalsare transmitted using multiple SS blocks, SS block ID of SS block inwhich the UE 501 has received the synchronization signal or referencesignal with best signal quality is reported instead of DL TX beam ID. Atoperation 516, the MeNB 502 then transmits the received ‘Best DL TX BeamID’ or SS block ID by including it in the SeNB Reconfiguration Complete.

At operation 517, the RACH Preamble is transmitted from the UE 501 tothe SeNB 503. At operation 517 a, the UE 501 transmits the RACHPreambles using the TX Beam corresponding to (i.e., in same directionas) ‘Best RX Beam’ wherein the ‘Best RX Beam’ is the beam used toreceive the ‘Best DL TX Beam’ or ‘Best RX Beam’ is the beam used toreceive the SS block in which the UE has received the synchronizationsignal or reference signal with best signal quality. At operation 517 b,the reception of the RACH Preamble by the SeNB 503 is done using the RXBeam corresponding to (i.e., in same direction as) the ‘Best DL TX Beam’or SS Block which is reported by the UE 501.

At operation 518, the RAR is then transmitted from the SeNB 503 to theUE 501. At operation 518 a, The SeNB 503 transmits the RAR using the‘Best DL TX Beam’ reported by the UE 501. In an embodiment in which SSblock ID is reported by the UE 501, the SeNB 503 transmits the RAR usingthe DL TX Beam which is used by the eNB for transmitting synchronizationsignal or reference signal in the SS block corresponding to SS block ID.At operation 518 b, the UE 501 receives the RAR using the identified‘Best RX Beam’ that is used to receive the ‘Best DL TX Beam’ or ‘Best RXBeam’ is the beam used to receive the SS block in which the UE hasreceived the synchronization signal or reference signal with best signalquality. The TA and SFN information may be included in the RAR. Systemframe number is the radio frame number of the radio frame in which theRAR is transmitted/received by the eNB/UE. This information can be usedby the UE 501 to synchronize with system frame number timing of the SeNB503. The UE 501 is not required to read the physical broadcast channel(which carries master information block) of the SeNB 503.

Embodiment 2 (Beam Feedback+Slot)

This Method of the disclosure is illustrated in FIG. 6 according to anembodiment of the present disclosure.

FIG. 6 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure.

Referring to FIG. 6, at operation 611, when an LF-BS (MeNB) 602 adds anHF-BS (SeNB) 603 for a UE 601, the MeNB 602 sends the SeNB AdditionRequest to the SeNB 603. At operation 612, the SeNB 603 in the responsesends the SeNB Addition Request Ack and includes the ‘HF RACH config’which carries all the parameters required for efficient RACH operationover the HF-BS. At operation 613, the MeNB 602 then sends the RRCConnection Reconfiguration to the UE 601 including the ‘HF RACH config’received from the SeNB 603. According to various examples, the HF RACHConfig may be broadcasted by the MeNB 602, or the HF RACH Config isdivided in two parts: HF RACH Config Common and HF RACH ConfigDedicated. The Common information is broadcasted by the MeNB 602, andthe dedicated information is sent in dedicated signaling from the SeNB603 to the UE 601 via the MeNB 602.

At operation 614, the UE 601 performs the DL measurement of the HF celland identifies the ‘Best DL TX beam’ and the corresponding ‘best RXbeam’ wherein the ‘Best DL TX beam’ refers to the DL beam transmitted bythe SeNB 603 which is received best by the UE 601 and the ‘Best RX beam’refers to the RX beam used by the UE 601 for the reception of the ‘BestDL TX beam’. The UE 601 basically searches for the best TX-RX beam pairamong the set of TX beams transmitted by the SeNB 603 and the set of RXbeams used by the UE 601 for the reception of the TX beams transmittedby the SeNB 603. At operation 615, the UE 601 identifies the ‘Best DL TXBeam’ and sends the ID of the identified ‘Best DL TX Beam’ (′Best DL TXBeam ID′) to the SeNB 603 via the MeNB 602 by including it in the RRCConnection Reconfiguration Complete message that it sends to the MeNB602. At operation 616, the MeNB 602 then forwards the received ‘Best DLTX Beam ID’ to the SeNB 603. In alternate embodiment wherein Downlinksynchronization signals or reference signals are transmitted usingmultiple SS blocks, SS block ID of SS block in which the UE 601 hasreceived the synchronization signal or reference signal with best signalquality is reported instead of DL TX beam ID. Best DL TX beam or SSblock ID reported by the UE is used by the SeNB 603 for receiving RACHpreamble from the UE 601.

At operation 617, the RACH Preamble is transmitted from the UE 601 tothe SeNB 603. At operation 617 b, the SeNB 603 receives RACH preamblefrom the corresponding the UE 601 using the ‘RX Beam’ corresponding to(i.e., in same direction as) the ‘Best DL TX Beam ID’ reported by the UE601. In embodiment in which SS block ID is reported instead of DL TXBeam ID, the SeNB 603 receives RACH preamble using RX beam reciprocal orin same direction as the DL TX Beam used by the eNB in the SS blockidentified by SS block ID reported by the UE 601. At operation 617 a,the transmission of the RACH by the UE 601 is done in the dedicatedtransmission RACH slots assigned by the SeNB 603 as indicated in the ‘HFRACH config’. The SeNB 603 also uses the corresponding indicateddedicated slots for the reception of the RACH preamble from the UE 601.

At operation 618, the RAR is then transmitted from the SeNB 603 to theUE 601. At operation 618 a, the SeNB 603 transmits the RAR using the‘Best DL TX Beam ID’ reported by the UE 601 in the dedicated slots asindicated in the HF RACH Config. In an embodiment in which SS block IDis reported by the UE, the SeNB 303 transmits the RAR using the DL TXBeam which is used by the eNB for transmitting the synchronizationsignal or reference signal in the SS block corresponding to SS block ID.At operation 618 b, the UE 601 receives the RAR on the slots asindicated in the HF RACH Config using its ‘Best RX beam’ that it hadidentified as the best RX beam for the reception of the identified ‘BestDL TX beam’ or SS block. The TA and SFN information may be included inthe RAR. System frame number is the radio frame number of the radioframe in which the RAR is transmitted/received by the eNB/UE. Thisinformation can be used by the UE 601 to synchronize with system framenumber timing of the SeNB 603. The UE 601 is not required to read thephysical broadcast channel (which carries master information block) ofthe SeNB 603.

In another embodiment of the present disclosure, the RAR is sent by theSeNB 603 at a slot relative to the slot on which the RACH Preamble isreceived. The UE 601 also receives the RAR on the slot relative to sloton which it had transmitted the RACH Preamble.

In one or more of the embodiments of the present disclosure, the timingsspecified in the HF RACH configuration are with respect to the MeNBtiming.

FIG. 7 is a schematic diagram illustrating transmission of a randomaccess preamble according to an embodiment of the present disclosure.

In existing system dedicated RACH slot is configured to avoid RACHcollision. Referring to FIG. 7, RACH slot is configured/indicated in thedisclosure so that the eNB can use specific RX beam (based on TX beam IDor SS block ID indicated by the UE) in the indicated slot. In theabsence of it, even the UE transmits using one beam, it has to transmitit multiple times for each RX beam of BS. Slots can be configured usingone of the following options:

Option 1: One dedicated slot 700: the UE transmit RACH preamble in thisslot and the eNB receives in this RACH slot.

Option 2: Multiple slots 705: Dedicated slot for each DL TX beam ID orSS block ID is provided. The UE transmit in the slot corresponding tothe best DL TX beam ID or SS block ID of SS block in which the UE hasreceived the synchronization signal or reference signal with best signalquality.

In addition to the preceding embodiment as illustrated in FIG. 7, morethan one slot can be assigned for the transmission of the RACH Preambleby the SeNB to the UE in the HF RACH Config. The UE transmits the RACHPreamble using the TX Beam(s) corresponding to its ‘Best RX Beam’wherein the ‘Best RX Beam’ is the RX Beam corresponding to the ‘Best DLTX Beam’ or ‘Best RX Beam’ is the beam used to receive the SS block inwhich the UE has received the synchronization signal or reference signalwith best signal quality. A UE may typically need to transmit the RACHusing multiple TX beams if due to different Beam widths in the RX and TXthere are more than one TX Beams corresponding to one RX Beam assumingthat the RX Beam width of the UE is greater than the TX Beam width ofthe SeNB.

In another variant of the preceding embodiment of the presentdisclosure, a mapping of TX Beam ID(s) or SS block ID(s) to the slots isspecified. The UE transmits the PRACH TX in a slot as per the assignedmapping. The mapping can be assigned by the SeNB in the HF RACH Config.

The ‘HF RACH Config’ as used in the various embodiments consists ofinformation pertaining to the HF cell (HF-BS/SeNB) which is useful forthe UE for efficiently performing Random Access on the SeNB subsequentto the addition of the SeNB. The ‘HF RACH Config’ contains at least oneof ‘RACH slot configuration’, ‘RAR Slot Configuration’, ‘PreambleConfiguration’, Timing Information’, ‘SeNB Beamforming Capability’ and‘Beamforming Gain’, wherein the ‘RACH Slot Configuration’ includes the‘Dedicated RACH slot for preamble TX/RX’ or the RACH slots correspondingto each DL TX beam’, and the ‘Preamble Configuration’ includes the‘Preamble Sequence’ and the ‘Preamble Valid Duration’, and the ‘TimingInformation’ includes the frame and/or subframe offset between the MeNBand the SeNB, and the ‘SeNB Beamforming Capability’ indicates the Numberof TX and RX Beams of the SeNB.

In an embodiment of the present disclosure, the MeNB indicates to the UEwhether the RAR will be transmitted by the MeNB or the SeNB. In case ofidea backhaul, the MeNB indicates that the RAR will be transmitted bythe MeNB, otherwise, by the SeNB. After transmitting the RACH preamble,the UE monitors the UE-MeNB link for the RAR if the MeNB indicates so,otherwise the UE monitors the UE-SeNB link for the RAR. Alternately, theMeNB may indicate to the UE whether the RAR for RACH transmission onfrequency F1 will be transmitted by cell on frequency F2.

In yet another embodiment of the present disclosure, the SeNB provides amapping between the RACH slot in the SeNB to the corresponding slot onthe MeNB where the RAR will be transmitted in the scenario where the RARis transmitted via the MeNB.

In an embodiment of the present disclosure, the contents of the mmW RACHConfig can be partitioned into ‘Common’ and ‘Dedicated’ wherein thecommon part is broadcasted. The Common part can include at least one ofRACH slots corresponding to each DL TX Beam, TX/RX Beamforming Gain, aNumber of RX Beams of the eNB, a Number of TX beams of the eNB, Timingoffset between the MeNB and the SeNB including the Frame Offset,subframe offset and slot offset.

Method 4:

Embodiment 1 (No Beam Feedback)

This Method of the disclosure is illustrated in FIG. 8 according to anembodiment of the present disclosure.

FIG. 8 is a signal flow diagram illustrating a method for a beamformedrandom access procedure according to an embodiment of the presentdisclosure.

Referring to FIG. 8, at operation 811, when an LF-BS (MeNB) 802 adds anHF-BS (SeNB) 803 for a UE 801, the MeNB 802 sends the SeNB AdditionRequest to the SeNB 803. At operation 812, the SeNB 803 in the responsesends the SeNB Addition Request Ack and includes the ‘HF RACH config’which carries all the parameters required for efficient RACH operationover the HF-BS. At operation 813, the MeNB 802 then sends the RRCConnection Reconfiguration to the UE 801 including the ‘HF RACH config’received from the SeNB 803. According to various examples, the HF RACHConfig may be broadcasted by the MeNB 802, or the HF RACH Config isdivided in two parts: HF RACH Config Common and HF RACH ConfigDedicated. The Common information is broadcasted by the MeNB 802, andthe dedicated information is sent in dedicated signaling from the SeNB803 to the UE 801 via the MeNB 802. At operation 814, the UE 801 sendsthe RRC Connection Reconfiguration Complete message. At operation 815,the MeNB 802 sends the SeNB Reconfiguration Complete.

At operation 816, the UE 801 performs the DL measurement of the HF celland identifies the ‘Best DL TX beam’ and the corresponding ‘best RXbeam’ wherein the ‘Best DL TX beam’ refers to the DL beam transmitted bythe SeNB 803 which is received best by the UE 801 and the ‘Best RX beam’refers to the RX beam used by the UE 801 for the reception of the ‘BestDL TX beam’. The UE 801 basically searches for the best TX-RX beam pairamong the set of TX beams transmitted by the SeNB 803 and the set of RXbeams used by the UE 801 for the reception of the TX beams transmittedby the SeNB 803.

At operation 817, the RACH Preamble is transmitted from the UE 801 tothe SeNB 803. At operation 817 a, the UE transmits the RACH Preambleusing the TX Beam corresponding to (i.e., in same direction as) the BestRX Beam wherein the ‘Best RX Beam’ is the RX Beam corresponding to the‘Best DL TX Beam’ or ‘Best RX Beam’ is the beam used to receive the SSblock (downlink synchronization signals are transmitted using multipleSS blocks) in which the UE has received the synchronization signal orreference signal with best signal quality. Transmission of RACH Preambleis repeated ‘N’ times wherein N is the Number of RX Beams at the SeNB803. N is signaled to the UE either in broadcast or dedicated signaling.At operation 817 b, the reception of the RACH Preamble at the SeNB 803is performed using multiple RX Beams as per the SeNB capability.

At operation 818, the RAR is then transmitted from the SeNB 803 to theUE 801. At operation 818 a, the SeNB 803 transmits the RAR using the TXBeam corresponding to the Best RX Beam identified based on the receptionof RACH Preamble using multiple RX Beams. At operation 818 b, the UE 801receives the RACH Preamble using the ‘Best RX Beam’ as identified duringthe measurement of the SeNB 803. The TA and SFN information may beincluded in the RAR. System frame number is the radio frame number ofthe radio frame in which the RAR is transmitted/received by the eNB/UE.This information can be used by the UE 801 to synchronize with systemframe number timing of the SeNB 803. The UE 801 is not required to readthe physical broadcast channel (which carries master information block)of the SeNB 803.

Embodiment 2 (No Beam Feedback+Slots)

This Method of the disclosure is illustrated in FIGS. 9A and 9Baccording to an embodiment of the present disclosure.

FIGS. 9A and 9B are signal flow diagrams illustrating a method for abeamformed random access procedure according to an embodiment of thepresent disclosure.

Referring to FIGS. 9A and 9B, at operation 911, when an LF-BS (MeNB) 902adds an HF-BS (SeNB) 903 for a UE 901, the MeNB 902 sends the SeNBAddition Request to the SeNB 903. At operation 912, the SeNB 903 in theresponse sends the SeNB Addition Request Ack and includes the ‘HF RACHconfig’ which carries all the parameters required for efficient RACHoperation over the HF-BS. At operation 913, the MeNB 902 then sends theRRC Connection Reconfiguration to the UE 901 including the ‘HF RACHconfig’ received from the SeNB 903. According to various examples, theHF RACH Config may be broadcasted by the MeNB 902, or the HF RACH Configis divided in two parts: HF RACH Config Common and HF RACH ConfigDedicated. The Common information is broadcasted by the MeNB 902, andthe dedicated information is sent in dedicated signaling from the SeNB903 to the UE 901 via the MeNB 902. At operation 914, the UE 901 sendsthe RRC Connection Reconfiguration Complete message. At operation 915,the MeNB 902 sends the SeNB Reconfiguration Complete.

At operation 916, the UE 901 performs the DL measurement of the HF celland identifies the ‘Best DL TX beam’ and the corresponding ‘best RXbeam’ wherein the ‘Best DL TX beam’ refers to the DL beam transmitted bythe SeNB 903 which is received best by the UE 901 and the ‘Best RX beam’refers to the RX beam used by the UE 901 for the reception of the ‘BestDL TX beam’. The UE 901 basically searches for the best TX-RX beam pairamong the set of TX beams transmitted by the SeNB 903 and the set of RXbeams used by the UE 901 for the reception of the TX beams transmittedby the SeNB 903.

At operation 917, the RACH Preamble is transmitted from the UE 901 tothe SeNB 903. At operation 917 a, the UE transmits the RACH Preambleusing the TX Beam corresponding to the Best RX Beam wherein the ‘Best RXBeam’ is the RX Beam corresponding to the ‘Best DL TX Beam’.Transmission of RACH Preamble is repeated ‘N’ times wherein N is theNumber of RX Beams at the SeNB 903. At operation 917 b, the reception ofthe RACH Preamble at the SeNB 903 is performed using multiple RX Beamsas per the SeNB capability.

According to this embodiment of the present disclosure, the transmissionof the RACH by the UE 901 is done in the dedicated transmission RACHslots assigned by the SeNB 903 as indicated in the ‘HF RACH config’. TheSeNB 903 also uses the corresponding indicated dedicated slots for thereception of the RACH preamble from the UE 901. The RACH Preambletransmission is repeated for N times where N is number of RX Beams atthe SeNB 903. N is signaled to the UE 901 either in broadcast ordedicated signaling.

At operation 918, the RAR is then transmitted from the SeNB 903 to theUE 901. At operation 918 a, after the receipt of the beamformed RACHpreamble from the UE using multiple RX Beams on the dedicated slots asindicated in the HF RACH Config, the SeNB 903 transmits the RAR usingthe using TX Beam corresponding to Best RX Beam for RACH reception inthe dedicated slots as indicated in the HF RACH Config. At operation 918b, the UE 901 receives the RAR on the slots as indicated in the HF RACHConfig using its ‘Best RX beam’ that it had identified as the best RXbeam for the reception of the identified ‘Best DL TX beam’ or SS block.The TA and SFN information may be included in the RAR. System framenumber is the radio frame number of the radio frame in which the RAR istransmitted/received by the eNB/UE. This information can be used by theUE 901 to synchronize with system frame number timing of the SeNB 803.The UE 901 is not required to read the physical broadcast channel (whichcarries master information block) of the SeNB 903.

FIG. 10 is a schematic diagram illustrating transmission of a randomaccess preamble according to an embodiment of the present disclosure.

Referring to FIG. 10, a mapping between the RACH slots and the RX beamof the SeNB is provided in the HF RACH Config and a mapping between theRAR slots and the TX Beams or SS blocks of the SeNB is provided. The UEbased on this information, transmits RACH Preamble using selected TXBeam in slots corresponding to each RX beam of the SeNB.

In another variant of the embodiment of the present disclosure, the RARis sent by the SeNB at a slot relative to the slot on which the RACHPreamble is received. The UE also receives the RAR on the slot relativeto slot on which it had transmitted the RACH Preamble.

In embodiments of the present disclosure, the eNB indicates a set ofslots for RACH preamble wherein the number of indicated slots is equalto the number of RX beams of the eNB, so that even if the UE has notreported the best DL beam feedback, the UE sends the RACH on the UL beamcorresponding to the best DL TX beam or SS blocks on each of theindicated slots and the eNB receives them using each RX beam.

In an embodiment of the present disclosure, the RAR can be transmittedusing same beam as many times as the number of the RX beams at the UEand received by the UE using multiple RX beams

In an embodiment of the present disclosure wherein RACH Preamble or RARis sent on multiple slots using a single selected beam, a starting slotis indicated to the UE.

In one variant of the embodiment of the present disclosure, theselection of the TX Beam by the SeNB for the RAR transmission is donebased on the identification of the ‘Best RX Beam’ corresponding to thebeams on which RACH Preamble is received wherein the selection of theBest RX Beam is done based on RSRP/RSSI measurements. The TX Beam ischosen as the one that corresponds to the selected Best RX Beam.

In another variant of the embodiment of the present disclosure, theselection of the TX Beam by the SeNB for the RAR transmission is donebased on the selection of any RX Beam amongst the set of RX Beams onwhich RACH Preamble is received. The TX Beam is chosen as the one thatcorresponds to the selected RX Beam.

In another variant of the embodiment of the present disclosure, the SeNBselects TX beams corresponding to all the RX beams on which the RACHPreamble is received. The RAR is sent on all the selected TX Beams.

The ‘HF RACH Config’ as used in the various embodiments consists ofinformation pertaining to the HF cell (HF-BS/SeNB) which is useful forthe UE for efficiently performing Random Access on the SeNB subsequentto the addition of the SeNB. The ‘HF RACH Config’ contains at least oneof: Dedicated Preamble Configuration, i.e., Preamble Sequence, PreambleValid Duration, Beam formed RACH Slot Configuration: RACH slotscorresponding to each RX beam of the eNB, Beam formed RAR SlotConfiguration: RAR slots corresponding to each TX beam of the eNB orDedicated RAR slot, TX/RX beamforming gain, Timing offset betweenframe/subframe of the MeNB and slot of the SeNB, and SFN info in the RARif BCH is not supported in HF Cell.

Method 5:

This method of the disclosure is illustrated in FIGS. 11A and 11Baccording to an embodiment of the present disclosure.

FIGS. 11A and 11B are signal flow diagrams illustrating a method for abeamformed random access procedure according to an embodiment of thepresent disclosure.

Referring to FIGS. 11A and 11B, at operation 1111, when an LF-BS (MeNB)1102 adds an HF-BS (SeNB) 1103 for a UE 1101, the MeNB 1102 sends theSeNB Addition Request to the SeNB 1103. At operation 1112, the SeNB 1103in the response sends the SeNB Addition Request Ack and includes the ‘HFRACH config’ which carries all the parameters required for efficientRACH operation over the HF-BS. At operation 1113, the MeNB 1102 thensends the RRC Connection Reconfiguration to the UE 1101 including the‘HF RACH config’ received from the SeNB 1103. According to variousexamples, the HF RACH Config may be broadcasted by the MeNB 1102, or theHF RACH Config is divided in two parts: HF RACH Config Common and HFRACH Config Dedicated. The Common information is broadcasted by the MeNB1102, and the dedicated information is sent in dedicated signaling fromthe SeNB 1103 to the UE 1101 via the MeNB 1102.

At operation 1114, the UE 1101 performs the DL measurement of the HFcell and identifies the ‘Best DL TX beam’ and the corresponding ‘best RXbeam’ wherein the ‘Best DL TX beam’ refers to the DL beam transmitted bythe SeNB 1103 which is received best by the UE 1101 and the ‘Best RXbeam’ refers to the RX beam used by the UE 1101 for the reception of the‘Best DL TX beam’. The UE 1101 basically searches for the best TX-RXbeam pair among the set of TX beams transmitted by the SeNB 1103 and theset of RX beams used by the UE 1101 for the reception of the TX beamstransmitted by the SeNB 1103.

At operation 1115, the UE 1101 reports the identified ‘Best DL TX BeamID’ only if the Mobility State of the UE 1101 is below a pre-configuredthreshold. For example, if the Mobility State of the UE 1101 isidentified to be ‘Low’ then only the UE 1101 reports the identified‘Best DL TX Beam ID’ because in case of high mobility the Selected ‘BestDL TX Beam ID’ can change prior to the completion of the RACH procedure.In alternate embodiment wherein Downlink synchronization signals aretransmitted using multiple SS blocks, SS block ID of SS block in whichthe UE 1101 has received the synchronization signal with best signalquality is reported instead of DL TX beam ID. The ‘Best DL TX Beam ID’or SS block ID is included in the RRC Connection ReconfigurationComplete message. At operation 1116, the MeNB 1102 then forwards thereceived ‘Best DL TX Beam ID’ or SS block ID to the SeNB 1103.

At operations 1117 and 1118, the UE 1101 and the SeNB 1103 performs theRACH reception and RAR transmission based on whether it has received the‘Best DL TX Beam ID’ or SS block ID if reported by the UE 1101 or not.At operation 1117 a, if the UE 1101 has reported the ‘Best DL TX BeamID’ then it transmits the RACH Preamble using the TX Beam correspondingto the ‘Best RX Beam’ wherein the ‘Best RX Beam’ is the RX Beamcorresponding to the selected ‘Best DL TX Beam ID’. If the UE hasreported the ‘SS block ID’ then it transmits the RACH Preamble using theTX Beam corresponding to the ‘Best RX Beam’ wherein the ‘Best RX Beam’is the RX Beam used to receive the SS block corresponding to reported SSblock ID. At operation 1117 a, if the UE has not reported the ‘Best DLTX Beam ID’ or SS block ID then it transmits the RACH Preamble using theTX Beam corresponding to the Best RX Beam wherein the ‘Best RX Beam’ isthe RX Beam corresponding to the ‘Best DL TX Beam’ or ‘Best RX Beam’ isthe RX Beam corresponding to SS block in which the UE has receivedsynchronization or reference signal with best signal quality. Thetransmission of RACH Preamble is repeated ‘N’ times wherein N is theNumber of RX Beams at the SeNB. At operation 1117 b, the SeNB 1103 uponreception of the ‘Best DL TX Beam ID’ reported by the UE 1101 utilizesthis information for reception of the RACH preamble from thecorresponding UE 1101 using the ‘RX Beam’ corresponding to the ‘Best DLTX Beam ID’ reported by the UE 1101. The SeNB 1103 upon reception of the‘SS Block ID’ reported by the UE 1101 utilizes this information forreception of the RACH preamble from the corresponding UE 1101 using the‘RX Beam’ corresponding to the ‘DL TX Beam’ of SS block reported by theUE 1101. The transmission of the RACH by the UE 1101 is done in thededicated transmission RACH slots assigned by the SeNB 1103 as indicatedin the ‘HF RACH config’. The SeNB 1103 also uses the correspondingindicated dedicated slots for the reception of the RACH preamble fromthe UE 1101. At operation 1117 b, if the UE has not reported the ‘BestDL TX Beam ID’ or SS block ID, the SeNB receives the RACH Preamble usingmultiple RX Beams as per the SeNB capability.

At operation 1118 a, after the receipt of the beamformed RACH preamblefrom the UE 1101, the SeNB 1103 transmits the RAR using the ‘Best DL TXBeam ID’ reported by the UE 1101 or using the ‘DL TX Beam’ of SS blockreported by the UE 1101 in the dedicated slots as indicated in the HFRACH Config. If the best DL TX beam ID or SS Block ID is not reported bythe UE, then The SeNB 1103 transmits the RAR using the TX Beamcorresponding to the Best RX Beam identified based on the reception ofRACH Preamble using multiple RX Beams.

At operation 1118 b, the UE 1101 receives the RAR using on the slots asindicated in the HF RACH Config its ‘Best RX beam’ that it hadidentified as the best RX beam for the reception of the identified ‘BestDL TX beam’ or SS block. On the other hand if the UE 1101 has notreported the ‘Best DL TX Beam ID’ or SS block ID then it transmits theRACH Preamble using the TX Beam corresponding (i.e., in same directionas) to the Best RX Beam wherein the ‘Best RX Beam’ is the RX Beamcorresponding to the ‘Best DL TX Beam’ or ‘Best RX Beam’ is the RX Beamcorresponding to SS block in which the UE has received synchronizationor reference signal with best signal quality.

The UE 1101 receives the RACH Preamble using the ‘Best RX Beam’ asidentified during the measurement of the SeNB 1103. Further as inpreceding embodiments of the present disclosure, the HF RACH Config caninclude the slot information for transmission of the RACH and forreception of the RAR. In addition a mapping between the RACH slots andthe RX beam of the SeNB 1103 and a mapping between the RAR slots and theTX Beams of the SeNB 1103 is provided in the HF RACH Config. The TA andSFN information may be included in the RAR.

The ‘HF RACH Config’ as used in the various embodiments consists ofinformation pertaining to the HF cell (HF-BS/SeNB) which is useful forthe UE for efficiently performing Random Access on the SeNB subsequentto the addition of the SeNB. The ‘HF RACH Config’ contains at least oneof: Dedicated Preamble Configuration, i.e., Preamble Sequence, PreambleValid Duration, Beam formed RACH Slot Configuration: RACH slotscorresponding to each RX beam of the eNB, Beam formed RAR SlotConfiguration: RAR slots corresponding to each TX beam of the eNB orDedicated RAR slot, TX/RX beamforming gain, Timing offset betweenframe/subframe of the MeNB and slot of the SeNB, and SFN info in the RARif BCH is not supported in HF Cell.

Method 6

In another embodiment of the present disclosure, the eNB indicates thenumber of TX beams that are to be used for sending of the RACH Preamblein mmW RACH Config for example, based on the RX BW and TX BW used at theUE Similar to the preceding embodiments of the present disclosure, theeNB can also indicate the slots corresponding to the transmission ofRACH on each beam.

It is to be noted that in methods 1 to 6, in case of a handover, the UEwill not send an RRCConnectionReconfiguration complete message to theMeNB after receiving the RRCConnectionReconfiguration message from theMeNB. The MeNB will not send RRCConnectionReconfiguration message to theSeNB. In case of a handover, the MeNB is a source eNB and the SeNB is atarget eNB. The rest of the procedure is the same.

In a plurality of the embodiment of the present disclosure, a RARIdentification in Contention based Random Access in Beamformed System isprovided.

Random access procedure is illustrated in FIGS. 12A and 12B according toan embodiment of the present disclosure.

FIGS. 12A and 12B are signal flow diagrams illustrating a random accessprocedure based on channel reciprocity according to an embodiment of thepresent disclosure.

Referring to FIGS. 12A and 12B, a UE 1201 measures the beamformed beammeasurement signal (SS, RS, and the like) transmitted by a BS 1202 anddetermines the best DL RX beam at operation 1211. At operation 1212, theUE 1201 transmits the PRACH using UL TX beam corresponding to (i.e., insame direction as) best DL RX beam at operation 1212 a. The UE 1201transmits PRACH in RACH slot X, wherein PRACH is transmitted using UL TXbeam multiple times. At operation 1212 b, the BS monitors the RACH slotX using multiple RX beams.

At operations 1213 and 1214, physical downlink control channel (PDCCH)and the RAR are transmitted by the BS 1202 using a TX beam 5corresponding to (i.e., in same direction as) a RX beam 5 for examplewherein BS 1202 has received the PRACH preamble using RX beam 5. Aftertransmitting the PRACH in RACH slot X, the UE monitors for PDCCH for theRAR using best DL RX beam during the RAR window at operation 1213 a. Ifa PRACH preamble is received using the RX beam 5, then the BS 1202transmits the RAR using the corresponding TX beam 5 at operation 1214 a.The RAR includes TA and grant.

At operation 1215, MSG 3 is transmitted by the UE 1201 to the BS 1202.If a RAR corresponding to the UE's PRACH (preamble ID in the RARcorresponds to PRACH preamble transmitted by the UE) is received, the UE1201 transmits MSG3 using the UL TX beam used to transmit PRACH atoperation 1215 a. MSG 3 may include best DL TX beam ID or SS block ID.If downlink synchronization signals or reference signals are transmittedusing multiple SS blocks, SS block ID of SS block in which the UE 1201has received the synchronization signal or reference signal with bestsignal quality may be included in MSG3. At operation 1215 b, the BS 1202receives MSG 3 in grant using RX beam with which the BS 1202 hasreceived the PRACH. BS 1202 receives the MSG3 using the RX beam used toreceive the PRACH.

At operation 1216 and 1217, PDCCH and MSG 4 are transmitted by the BS1202 using a TX beam 5 corresponding to a RX beam 5 for example. Aftertransmitting the MSG 3, the UE 1201 monitors PDCCH for MSG 4 using bestDL RX beam at operation 1216 a. On receiving the MSG 3, the BS 1202transmits MSG 4 using TX beam with which the BS 1202 has transmitted theRAR or using TX beam indicated in MSG 3 at operation 1217 a. If SS blockID is indicated in MSG3, the BS 1202 transmits MSG4 using TX beam whichthe BS 1202 has used for transmitting Downlink synchronization signalsor reference signals in SS block identified by SS block.

One of the issues in the above procedure is illustrated in FIGS. 13A and13B according to an embodiment of the present disclosure.

FIGS. 13A and 13B are signal flow diagram illustrating a problem whenrandom access procedures are performed by multiple UEs with one basestation according to an embodiment of the present disclosure.

Referring to FIGS. 13A and 13B, at operations 1311 and 1312, the UE11301 and UE2 1303 transmit determines the best DL RX beam by measuring abeam measurement reference signal (BRS or SS). At operation 1313 and1314, the UE1 1301 and the UE2 1303 transmit the PRACH preamble in sameRACH slot X. At operation 1313 a, the UE1 1301 transmits the PRACH usingUL TX beam corresponding to best DL RX beam. At operation 1314 a, theUE2 1303 transmits the PRACH using UL TX beam corresponding to best DLRX beam. At operation 1313 b, the BS 1302 receives PRACH from both UEs1301, 1303 using different RX beam in RACH slot x. After transmittingthe PRACH in RACH slot X, UEs 1301, 1303 monitor for PDCCH for the RARusing each best DL RX beam during the RAR window at operations 1315 and1316.

At operations 1317 and 1317 a, the BS 1302 transmits RAR1 for UE2's RACHand RAR2 for UE1's RACH using TX beam 4 and TX beam 5, respectively,corresponding to PRACH preamble reception using RX beam 4 and RX beam 5.While monitoring PDCCH using best DL RX beam, each UE 1301, 1303 mayreceive transmission from multiple TX beams at operations 1317 b and1317 c. For example, the UE1 1301 can receive the RAR1 which is for UE2and processes it. This leads to transmission of MSG3 using incorrectgrant and TA and eventually leads to random access failure.

RAR Identification Method 1:

Embodiment 1

In an embodiment of the present disclosure, the issue of RARidentification can be resolved as illustrated in FIGS. 14A and 14Baccording to an embodiment of the present disclosure.

FIGS. 14A and 14B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct randomaccess response (RAR) according to an embodiment of the presentdisclosure.

Referring to FIGS. 14A and 14B, at operations 1411 and 1412, the UE11401 and UE2 1403 transmit determines the best DL RX beam by measuring aBRS or SS. At operations 1413 and 1414, the UE1 1401 and the UE2 1403transmit the PRACH preamble in same RACH slot X. At operation 1413 a,the UE1 1401 transmits the PRACH using UL TX beam corresponding to bestDL RX beam. At operation 1414 a, the UE2 1403 transmits the PRACH usingUL TX beam corresponding to best DL RX beam. At operation 1413 b, the BS1402 receives PRACH from both UEs 1401, 1403 using different RX beam inRACH slot x.

After transmitting the PRACH in RACH slot X, UEs 1401, 1403 monitor forPDCCH for the RAR using each best DL RX beam during the RAR window atoperations 1415 and 1416. In this embodiment of the present disclosure,at operations 1417 and 1418, the BS 1402 transmits PDCCHs which arecyclic redundancy check (CRC) masked with random access (RA)-radionetwork temporary identifiers (RNTIs). At operations 1417 a and 1418 a,each UE 1401, 1403 monitors (E) PDCCH for the RARs identified by theRA-RNTI defined below, in the RA response window which starts at fixedposition relative to subframe in which PRACH is transmitted and haslength configured by BS 1402.

In an embodiment of the present disclosure, each UE 1401, 1403 use theRA-RNTI=1+best DL TX beam ID (or SS block ID) for receiving the RAR. SSblock ID is the ID of SS block in which each UE 1401, 1403 has receivedthe synchronization or reference signal with best signal quality. ThePDCCH indicating the RAR is CRC masked by the BS 1402 with RA-RNTI=1+TXbeam ID (or SS block ID) wherein TX beam ID identifies the TX beam usedto transmit the PDCCH and the corresponding RAR. SS block ID is the IDof the SS block in which the BS 1402 transmits synchronisation orreference signal using the TX beam which is used for transmitting thePDCCH and the corresponding RAR.

Alternately, RA-RNTI=1+RX beam ID wherein RX beam ID is the beam ID ofthe RX beam with which the BS 1402 has received PRACH. The BS 1402provides mapping between its RX beam ID and TX beam ID(s) or SS blockIDs. Each UE 1401, 1403 know the best DL TX beam ID or SS block ID, soit can know BS RX beam ID based on above mapping. Accordingly each UE1401, 1403 knows the RA-RNTI for receiving the RAR.

The RA-RNTI associated with the PRACH in which the Random AccessPreamble is transmitted, can be computed as:

N+t_id+k1*f_id+k2*b_id,

Where,

t_id is the index of RACH slot e.g., subframe index of the firstsubframe of PRACH;

f_id is the index of the specified PRACH within that subframe, inascending order of frequency domain;

b_id is the beam index or SS block index; N is fixed offset, can be 1

0<=t_id<N1;0<=f_id<N2;0<=b_id<N3;

k1=1+t_id;k2=1+t_id+k1*f_id

N+t_id+k1*b_id,

Where, t_id is the index of RACH slot e.g., subframe index of the firstsubframe of PRACH

b_id is the beam index or SS block index; N is fixed offset, can be 1

0<=t_id<N1;0<=b_id<N2;k1=1+t_id;

N+f_id+k1*b_id,

Where,

f_id is the index of the specified PRACH within that subframe, inascending order of frequency domain,

b_id is the beam index; N is fixed offset, can be 1

0<=f_id<N1;0<=b_id<N2;k1=1+f_id;

In an embodiment of the present disclosure, b_id can be DL TX beam indexor SS block index, DL RX beam Index. In another embodiment of thepresent disclosure, both can be used in computing RA-RNTI.

At operations 1419 and 1420, the BS 1402 transmits RAR1 for UE2's RACHand RAR2 for UE1's RACH using TX beam 4 and TX beam 5 respectively, atoperation 1419 a.

PDCCH indicates DL assignment for the RAR. The UE processes the PDCCHcorresponding to its RA-RNTI as determined above. Each UE 1401, 1403decodes transport block (TB) and receives the RAR based on the DLassignment in the PDCCH processed at operations 1419 b and 1420 b.

After receiving the RAR, if the RAR includes the PRACH preamble ID, theneach of the UE 1401, 1403 considers this Random Access Responsereception successful. Each UE 1401, 1403 processes the TA received inthe RAR and transmits MSG3 using the received grant in the RAR.

Each UE 1401, 1403 may stop monitoring for Random Access Response(s)after successful reception of a Random Access Response containing RandomAccess Preamble identifiers that matches the transmitted Random AccessPreamble.

Embodiment 2

In another embodiment of the present disclosure, the issue of RARidentification can be resolved as illustrated in FIGS. 15A and 15Baccording to an embodiment of the present disclosure.

FIGS. 15A and 15B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure.

Referring to FIGS. 15A and 15B, at operations 1511 and 1512, the UE11501 and UE2 1503 transmit determines the best DL RX beam by measuring aBRS. At operations 1513 and 1514, the UE1 1501 and the UE2 1503 transmitthe PRACH preamble in same RACH slot X. At operations 1513 a and 1514 a,PRACH is transmitted using a TX beam once instead of transmittingmultiple times for RX sweeping at the BS 1502. There is one to mappingbetween RACH transmission opportunity and DL TX beam ID. The UE 1501transmits in RACH transmission opportunity corresponding to its best DLTX beam ID. Alternately, there is one to mapping between RACHtransmission opportunity and DL RX beam ID. Mapping between DL RX beamID and one or more DL TX beam IDs can be signaled to the UE or DL RXbeam ID can be same as DL TX beam ID. The UE transmit in RACHtransmission opportunity corresponding to its best DL TX beam ID. Atoperation 1513 b, the BS 1502 receives PRACH from both UEs 1501, 1503using different RX beam in RACH slot x.

After transmitting the PRACH in RACH slot X, UEs 1501, 1503 monitor forPDCCH for the RAR using each best DL RX beam during the RAR window atoperation 1515 and 1516. In this method, at operation 1517 and 1518, theBS 1502 transmits PDCCHs which are CRC masked with RA-RNTI. Atoperations 1517 a and 1518 a, each UE 1501, 1503 monitors (E) PDCCH forthe RARs identified by the RA-RNTI in the RA response window whichstarts at fixed position relative to subframe in which PRACH istransmitted and has length configured by BS 1502.

At operation 1519 and 1520, the BS 1502 transmits RAR1 for UE2's RACHand RAR2 for UE1's RACH using TX beam 4 and TX beam 5 respectively, atoperation 1519 a.

PDCCH indicates DL assignment for the RAR. The UE processes the PDCCHcorresponding to its RA-RNTI as determined above. Each UE determines itsRA-RNTI as explained in embodiment 1. Each UE 1501, 1503 decodes TB andreceives the RAR for each based on the DL assignment in the PDCCHprocessed at operations 1519 b and 1520 b.

RAR Identification Method 2

Embodiment 1

In an embodiment of the present disclosure, the issue of RARidentification can be resolved as illustrated in FIGS. 16A and 16Baccording to an embodiment of the present disclosure.

FIGS. 16A and 16B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure.

Referring to FIGS. 16A and 16B, at operations 1611 and 1612, the UE11601 and UE2 1603 transmit determines the best DL RX beam by measuring aBRS or SS. At operations 1613 and 1614, the UE1 1601 and the UE2 1603transmit the PRACH preamble in same RACH slot X. At operation 1613 a,the UE1 1601 transmits the PRACH using UL TX beam corresponding to bestDL RX beam. At operation 1614 a, the UE2 1603 transmits the PRACH usingUL TX beam corresponding to best DL RX beam. At operation 1613 b, the BS1602 receives PRACH from both UEs 1601, 1603 using different RX beam inRACH slot x.

After transmitting the PRACH in RACH slot X, UEs 1601, 1603 monitor forPDCCH for the RAR using each best DL RX beam during the RA responsewindow which starts at fixed position relative to subframe in whichPRACH is transmitted and has length configured by the BS 1602, atoperations 1615 and 1616. In this embodiment of the present disclosure,at operations 1617 and 1618, the BS 1602 transmits PDCCH in eachsubframe(s) corresponding to each DL TX beam ID using TX beam 4 and TXbeam 5 respectively at operation 1619 a. In the RAR window, each UE1601, 1603 monitors the subframe(s) corresponding to the UE's best DL TXbeam ID or SS block ID, at operations 1617 a and 1618 a. SS block ID isthe ID of SS block in which each UE 1601, 1603 has received thesynchronisation or reference signal with best signal quality.

One example of mapping between the subframe and DL TX beam ID (or SSblock ID) in the RAR window is illustrated in FIG. 17.

FIG. 17 is a schematic diagram illustrating identification of a RARaccording to an embodiment of the present disclosure.

Referring to FIG. 17, mapping between the subframe(s) in the RAR windowand the DL TX beam IDs (or SS block IDs) is signaled by the BS or it maybe fixed. Alternately, the subframe number corresponding to a beam ID(or SS block ID) can be equal to beam ID (or SS block ID) mod (Number ofsubframes in the RAR Window).

At operations 1619 and 1620, the BS 1602 transmits RAR1 for UE2's RACHand RAR2 for UE1's RACH using TX beam 4 and TX beam 5 in each subframecorresponding to each TX Beam ID (or SS block ID) in the RAR window. SSblock ID is the ID of the SS block in which the BS 1602 transmitssynchronisation or reference signal using the TX beam which is used fortransmitting the PDCCH and the corresponding RAR.

In an embodiment of the present disclosure, the RAR window can bedifferent for different DL TX beam and SS block. The UE monitors the RARwindow corresponding to its best DL TX beam or SS block ID of SS blockin which it has received the synchronisation or reference signal withbest signal quality.

PDCCH indicates DL assignment for the RAR. Each UE processes the PDCCHcorresponding to its RA-RNTI. Each UE 1601, 1603 decodes TB and receivesthe RAR based on the DL assignment of processed PDCCH at operations 1619b and 1620 b.

After receiving the RAR, if the RAR includes the PRACH preamble ID, theneach of the UE 1601, 1603 considers this Random Access Responsereception successful. Each UE 1601, 1603 processes the TA received inthe RAR and transmits MSG3 using the received grant in the RAR.

Each UE 1601, 1603 may stop monitoring for Random Access Response(s)after successful reception of a Random Access Response containing RandomAccess Preamble identifiers that matches the transmitted Random AccessPreamble.

Embodiment 2

In another embodiment of the present disclosure, the issue of RARidentification can be resolved as illustrated in FIGS. 18A and 18Baccording to an embodiment of the present disclosure.

FIGS. 18A and 18B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure.

Referring to FIGS. 18A and 18B, at operations 1811 and 1812, the UE11801 and UE2 1803 transmit determines the best DL RX beam by measuring aBRS. At operation 1813 and 1814, the UE1 1801 and the UE2 1803 transmitthe PRACH preamble in same RACH slot X. At operations 1813 a and 1814 a,PRACH is transmitted using a TX beam once instead of transmittingmultiple times for RX sweeping at the BS 1802. There is one to mappingbetween RACH transmission opportunity and DL TX beam ID (or SS blockID). The UE 1801 transmits in RACH transmission opportunitycorresponding to its best DL TX beam ID (or SS block ID). Alternately,there is one to mapping between RACH transmission opportunity and DL RXbeam ID. Mapping between DL RX beam ID and one or more DL TX beam IDscan be signaled to the UE or DL RX beam ID can be same as DL TX beam ID.The UE transmit in RACH transmission opportunity corresponding to itsbest DL TX beam ID (or SS block ID). At operation 1813 b, the BS 1802receives PRACH from both UEs 1801, 1803 using different RX beam in RACHslot x.

After transmitting the PRACH in RACH slot X, UEs 1801, 1803 monitor forPDCCH for the RAR using each best DL RX beam during the RA responsewindow which starts at fixed position relative to subframe in whichPRACH is transmitted and has length configured by the BS 1802, atoperations 1815 and 1816. In this embodiment of the present disclosure,at operations 1817 and 1818, the BS 1802 transmits PDCCH in eachsubframe(s) corresponding to each DL TX beam ID using TX beam 4 and TXbeam 5 respectively at operation 1819 a. In the RAR window, each UE1801, 1803 monitors the subframe(s) corresponding to the UE's best DL TXbeam ID, at operations 1817 a and 1818 a. One example of mapping betweenthe subframe and DL TX beam ID in the RAR window is illustrated in FIG.17. Mapping between the subframe in the RAR window and the DL TX beam IDis signaled by the BS or it may be fixed. Alternately, the subframenumber corresponding to a beam ID can be equal to beam ID mod (Number ofsubframes in the RAR Window).

At operations 1819 and 1820, the BS 1802 transmits RAR1 for UE2's RACHand RAR2 for UE1's RACH using TX beam 4 and TX beam 5 in each subframecorresponding to each TX Beam ID in RAR window.

PDCCH indicates DL assignment for the RAR. Each UE processes the PDCCHcorresponding to its RA-RNTI. Each UE 1801, 1803 decodes TB and receivesthe RAR based on the DL assignment of processed PDCCH at operations 1819b and 1820 b.

RAR Identification Method 3

Embodiment 1

In an embodiment of the present disclosure, the issue of RARidentification can be resolved as illustrated in FIGS. 19A and 19Baccording to an embodiment of the present disclosure.

FIGS. 19A and 19B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure.

Referring to FIGS. 19A and 19B, at operations 1911 and 1912, the UE11901 and UE2 1903 transmit determines the best DL RX beam by measuring aBRS. At operations 1913 and 1914, the UE1 1901 and the UE2 1903 transmitthe PRACH preamble in same RACH slot X. At operation 1913 a, the UE11901 transmits the PRACH using UL TX beam corresponding to best DL RXbeam. At operation 1914 a, the UE2 1903 transmits the PRACH using UL TXbeam corresponding to best DL RX beam. At operation 1913 b, the BS 1902receives PRACH from both UEs 1901, 1903 using different RX beam in RACHslot x.

After transmitting the PRACH in RACH slot X, UEs 1901, 1903 monitor forPDCCH for the RAR using each best DL RX beam during the RA responsewindow which starts at fixed position relative to subframe in whichPRACH is transmitted and has length configured by the BS 1902, atoperations 1915 and 1916. In this embodiment of the present disclosure,at operations 1917 and 1918, the BS 1902 transmits PDCCH containing adownlink control information (DCI) including the DL TX beam ID, using TXbeam 4 and TX beam 5 respectively at operation 1919 a. The DL TX beam IDincluded in the DCI is the beam ID of the DL TX beam used to transmitthe PDCCH containing this DCI. Alternately SS block ID may be includedin DCI instead of DL TX beam ID wherein SS block ID is the ID of the SSblock in which the BS transmits a synchronization or reference signalusing the TX beam which is used for transmitting the PDCCH and thecorresponding RAR.

In the RAR window, each UE 1901, 1903 monitors the PDCCH correspondingto the UE's best DL TX beam ID, at operations 1917 a and 1918 a.

At operations 1919 and 1920, the BS 1902 transmits RAR1 for UE2's RACHand RAR2 for UE1's RACH using TX beam 4 and TX beam 5 in the RAR window.

PDCCH indicates DL assignment for the RAR. Each UE processes the PDCCHcorresponding to its RA-RNTI. Each UE 1901, 1903 decodes TB and receivesthe RAR based on the DL assignment of processed PDCCH at operations 1919b and 1920 b.

Each UE 1901, 1903 processes the RAR and transmits MSG3 using theallocated grant if the DCI in associated PDCCH includes UE's best DL TXbeam ID (or SS block ID) and the RAR includes the PRACH preamble IDtransmitted by it. The BS 1902 includes the TX beam ID (or SS block ID)of the beam used to transmit PDCCH in the DCI of the PDCCH. SS block IDis the ID of the SS block in which the BS 1902 transmits synchronisationor reference signal using the TX beam which is used for transmitting thePDCCH and the corresponding RAR.

Embodiment 2

In another embodiment of the present disclosure, the issue of RARidentification can be resolved as illustrated in FIGS. 20A and 20Baccording to an embodiment of the present disclosure.

FIGS. 20A and 20B are signal flow diagrams illustrating a method for abeamformed random access procedure for identifying a correct RARaccording to an embodiment of the present disclosure.

Referring to FIGS. 20A and 20B, at operations 2011 and 2012, the UE12001 and UE2 2003 transmit determines the best DL RX beam by measuring aBRS. At operations 2013 and 2014, the UE1 2001 and the UE2 2003 transmitthe PRACH preamble in same RACH slot X. At operation 2013 a, the UE12001 transmits the PRACH using UL TX beam corresponding to best DL RXbeam. At operation 2014 a, the UE2 2003 transmits the PRACH using UL TXbeam corresponding to best DL RX beam. At operation 2013 b, the BS 2002receives PRACH from both UEs 2001, 2003 using different RX beam in RACHslot x.

After transmitting the PRACH in RACH slot X, UEs 2001, 2003 monitor forPDCCH for the RAR using each best DL RX beam during the RA responsewindow which starts at fixed position relative to subframe in whichPRACH is transmitted and has length configured by the BS 2002, atoperations 2015 and 2016. At operation 2017 and 2018, the BS 2002transmits PDCCH using TX beam 4 and TX beam 5 respectively at operation2019 a.

In this embodiment of the present disclosure, at operations 2019 and2020, the BS 2002 transmits RAR1 including TX beam ID 4 for UE2 and RAR2including TX beam ID 5 for UE1 using TX beam 4 and TX beam 5 in the RARwindow. DL TX beam ID (or SS block ID) can be included in the RAR. If aRAR is transmitted using DL TX beam X, DL TX beam ID X is included inthe RAR. BS 2002 includes in a RAR, DL TX beam ID of TX beam used totransmit this RAR. Alternately SS block ID may be included in the RARinstead of DL TX beam ID wherein SS block ID is the ID of the SS blockin which the BS transmits a synchronization or reference signal usingthe TX beam which is used for transmitting the PDCCH and thecorresponding RAR.

At operations 2017 a and 2018 a, UE1 2001 monitors the RAR including itsbest DL TX beam ID and UE2 2003 monitors the RAR including its best DLTX beam ID in the RAR window. PDCCH indicates DL assignment for the RAR.Each UE 2001, 2003 decodes TB and receives the RAR based on the DLassignment and the best TX beam at operations 2019 b and 2020 b. Each UE2001, 2003 processes the RAR if the RAR includes UE's best DL TX beam ID(or SS block ID) and the RAR includes the PRACH preamble ID transmittedby it. The BS 2002 includes the TX beam ID (or SS block ID) of the beamused to transmit PDCCH in the DCI of the PDCCH. SS block ID is the ID ofthe SS block in which the BS 2002 transmits synchronisation or referencesignal using the TX beam which is used for transmitting the PDCCH andthe corresponding RAR.

RAR Identification Method 4:

PDCCH indicates DL assignment for the RAR. The UE decodes TB andreceives the RAR based on this DL assignment. After receiving the RAR,if the RAR includes the PRACH preamble ID, then the UE considers thisRandom Access Response reception successful. In an embodiment of thepresent disclosure, even after receiving the RAR successfully, the UEmay continue to monitor for additional RAR corresponding to its PRACHtransmission in the RAR window(s). Network may configure whether the UEshould monitor for additional RAR(s) in the RAR window(s) or whether itshould stop monitoring RAR window(s) after receiving a RAR successfullyin broadcast or dedicated signaling. Network may also configure theevents or scenarios (e.g., handover, SR, TA, and the like) in which theUE should or should not monitor for multiple RARs in the RAR window(s).In case of latency sensitive event, the UE may not be configured tomonitor multiple RARs. There can be one or separate RAR window for eachPRACH transmission.

If the UE has received multiple RAR corresponding to its PRACHtransmission(s), then the UE selects one RAR and uses it for MSG3transmission. In an embodiment of the present disclosure, the UErandomly selects one RAR from received RARs. In another embodiment ofthe present disclosure, the UE selects the RAR which includes the totalradiated power (TRP) ID of the TRP whose DL synchronization signals orreference signals are received (or best received) by the UE or TRP ID ofthe TRP selected by the UE. In another embodiment of the presentdisclosure, the UE may select the RAR which is received with best signalquality amongst the all received RARs. In another embodiment of thepresent disclosure, the eNB may indicate the rank in the RAR. If the eNBreceives the same PRACH preamble using different RX beams then ittransmits the RAR for each of them and ranks those according to thesignal strength of received PRACH transmission from each RX beam. If theUE receives multiple RAR corresponding to its PRACH transmissions thenit selects the RAR with highest rank. In another embodiment of thepresent disclosure, the eNB may indicate the signal strength of receivedPRACH transmission in the RAR. If the eNB receives the same PRACHpreamble using different RX beams then it transmits the RAR for each ofthem and indicates the signal strength of received PRACH transmissionfrom each RX beam. If the UE receives multiple RAR corresponding to itsPRACH transmissions then it selects the RAR with highest signalstrength.

In an embodiment of the present disclosure, network may also indicateone above the methods (random, first, the RAR with strongest receivedpower, the RAR indicating the strongest signal quality of preamblereceived at the BS, and the like) the UE uses for selecting the RAR.

The UE processes the TA received in the RAR and transmits MSG3 using thereceived grant in the selected RAR.

In a plurality of the embodiment of the present disclosure, a PowerRamping during Random Access in Beamformed System is provided.

The UE retransmits the PRACH if it fails to receive the RAR aftertransmitting the PRACH. In traditional system power is ramped up forevery PRACH retransmission. In case of beamformed system, power shouldnot be ramped up for every retransmission.

The UE may be transmitting same beam for RX sweeping at the BS

PRACH transmission may fail because of incorrect beam

PRACH transmission may fail because of TX power being not enough

During the random access procedure, when the UE should ramp up powershould be defined.

Method 1

This method of the disclosure is illustrated in FIGS. 21 and 22according to an embodiment of the present disclosure.

FIG. 21 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIG. 21, a random access procedure comprises of one or moreRA Attempts. Maximum number of RA attempts is configurable by network(example by RRC signaling or in system information, and the like). Ineach RA attempt, the UE transmits PRACH preamble using same TX beam butit ramps up power for same TX beam multiple times. It is to be notedthat power is not ramped up for each PRACH preamble transmission in anRA attempt. During the PRACH preamble transmissions in RA attempt, ifthe UE repeats PRACH preamble transmission for RX beam sweeping at theBS, then the UE does not ramp up the power for these transmissions. Ifthe PRACH preamble transmission is not repeated for RX sweeping thenwithin a RA attempt, power is ramped up for each new PRACH preambletransmission.

RA attempt is shown in FIG. 21. The UE first determines the UL TX beamfor PRACH preamble transmission. In an embodiment of the presentdisclosure, the UE measures the beamformed beam measurement signal (orSS or CSI-RS) transmitted by BS and determines the best DL RX beam i.e.,UE's RX beam with which it is able to receive the DL signal with bestquality. The UE determines the UL TX beam reciprocal (i.e., same or insame direction) to the determined best DL RX beam for PRACH preambletransmission. The UE transmits PRACH preamble using the determined UL TXbeam one or more times using the power ‘P’ wherein the UE may transmitPRACH preamble multiple times for RX beam sweeping at the BS. The numberof times the UE repeats PRACH preamble transmission for RX sweeping canbe configured by network (example by RRC signaling or in systeminformation, and the like).

If the RAR is not received, the UE ramps up the power by Delta whereDelta is configured by network and transmits, using the same UL TX beam,one or more times using the power ‘P+Delta’ wherein the UE may transmitPRACH preamble multiple times for RX beam sweeping at the BS. If the RARis not received, the UE ramps up the power again by Delta where Delta isconfigured by network and transmits using the same UL TX beam one ormore times using the power ‘P+2*Delta’ wherein the UE may transmit PRACHpreamble multiple times for RX beam sweeping at the BS. The UE ramps upthe power and retransmits PRACH preamble using the same UL TX beam ‘N’times if the RAR is not received. ‘N’ times are configurable by network.

FIG. 22 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure.

Referring to FIG. 22, at operation 2201, the UE sets RA Attempt Counterto 1. At operation 2203, the UE determines the UL TX beam for PRACHpreamble transmission. At operation 2205, the UE sets PRACH PreambleTransmission Counter to 1.

At operation 2207, the UE calculates TX power according to TXpower=P+Power Ramping, based on:

P is an initial power

Power Ramping=(PRACH Preamble TransmissionCounter−1)*PowerRampingStep(i.e.,Delta)

At operation 2209, the UE transmit PRACH preamble one or multiple times(for RX sweeping at the BS) using the determined UL TX beam and thecalculated TX power.

At operation 2211, the UE determines that the RAR is successfullyreceived. If received, at operation 2213, it is determined as a randomaccess success. If not received, at operation 2215, the UE determineswhether the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER. If the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER, the UE then determines whether the RA Attempt Counter is equalto MAX Attempt COUNTER at operation 2217. If the RA Attempt Counter isequal to MAX Attempt COUNTER, it is determined as a random accessfailure at operation 2219. If the RA Attempt Counter is not equal to MAXAttempt COUNTER, the UE sets the RA Attempt Counter=RA AttemptCounter+1, at operation 2221. At operation 2223, the UE determine thatthe UL TX beam for PRACH transmission is changed. If changed, go backfor the operation 2205. If not changed, it is determined as a randomaccess failure at operation 2225. In an alternate embodiment of thepresent disclosure, after operation 2221 UEs go back for the operation2203.

If the Preamble Transmission Counter is not equal to MAX TX COUNTER, theUE sets the Preamble Transmission Counter=Preamble TransmissionCounter+1 at operation 2227, and then go back for the operation 2207.

The MAX TX Counter and the MAX Attempt Counter can be predefined orconfigured by network (example by RRC signaling or in systeminformation, and the like).

Method 2

This method of the disclosure is illustrated in FIGS. 23, 24 and 25according to an embodiment of the present disclosure.

FIG. 23 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIG. 23, the UE Ramp up the power for PRACH preambleretransmission irrespective of whether beam is changed. It is to benoted that during the PRACH preamble transmissions, if the UE repeatsPRACH preamble transmission for RX beam sweeping at the BS, then the UEdoes not ramp up the power for these transmissions.

The UE determines the UL TX beam for PRACH preamble transmission. In anembodiment of the present disclosure, the UE measures the beamformedbeam measurement signal (or SS or CSI-RS) transmitted by BS anddetermines the best DL RX beam i.e., the UE's RX beam with which it isable to receive the DL signal with best quality. The UE determines theUL TX beam reciprocal (i.e., same or in same direction) to determinedbest DL RX beam. The UE transmits PRACH preamble using determined UL TXbeam one or multiple times using the power ‘P’. After transmitting PRACHpreamble one or multiple times for RX sweeping and if the RAR is not yetreceived, the UE determines the UL TX beam for PRACH transmission againand retransmit PRACH preamble one or multiple times for RX sweepingusing the power ‘P+Delta’. After transmitting PRACH preamble one ormultiple times for RX sweeping using the power ‘P+Delta’ and if the RARis not yet received, the UE determines the UL TX beam for PRACHtransmission again and retransmit PRACH preamble one or multiple timesfor RX sweeping using the power ‘P+2Delta’. This process is repeateduntil the RAR is received or process is already repeated for N times.‘N’ times are configurable by network.

According to various examples, the UE can wait for the RAR aftertransmitting beam multiple times for RX beam sweeping partially. Forexample there are 10 RX beams at the BS, the UE transmits PRACH preambleusing a TX beam 5 times and then waits for the RAR. If the RAR is notreceived, the UE transmits PRACH preamble using TX beam for 5 moretimes.

FIG. 24 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure.

Referring to FIG. 24, at operation 2401, the UE sets PRACH PreambleTransmission Counter to 1. At operation 2403, the UE determines the ULTX beam for PRACH preamble transmission.

At operation 2405, the UE calculates TX power according to TXpower=P+Power Ramping, based on:

P is an initial power (Note that P can be calculated every time the UEprocesses operation 2405. In alternate embodiment of the presentdisclosure, it may be calculated only once i.e., when PRACH PreambleTransmission Counter equals one)

Power Ramping=(PRACH Preamble TransmissionCounter−1)*PowerRampingStep(i.e.,Delta)

At operation 2407, the UE transmits PRACH preamble one or multiple times(for RX sweeping at the BS) using the determined UL TX beam and thecalculated TX power.

At operation 2409, the UE determines that the RAR is successfullyreceived. If received, at operation 2411, it is determined as a randomaccess success. If not received, at operation 2413, the UE determineswhether the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER. If the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER, it is determined as a random access failure at operation 2415.If the PRACH Preamble Transmission Counter is not equal to MAX TXCOUNTER, the UE sets the PRACH Preamble Transmission Counter=PRACHPreamble Transmission Counter+1 at operation 2417, and then go back forthe operation 2403.

The MAX TX Counter can be predefined or can be configured by network(example by RRC signaling or in system information, and the like).

FIG. 25 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure.

Referring to FIG. 25, at operation 2501, the UE sets PRACH PreambleTransmission Counter to 1. At operation 2503, the UE determines the ULTX beam for PRACH preamble transmission.

At operation 2505, the UE calculates TX power according to TXpower=P+Power Ramping, based on:

P is an initial power (Note that P can be calculated every time the UEprocesses operation 2405. In alternate embodiment of the presentdisclosure, it may be calculated only once i.e., when PRACH PreambleTransmission Counter equals one)

Power Ramping=(PRACH Preamble TransmissionCounter−1)*PowerRampingStep(i.e.,Delta)

At operation 2507, the UE transmit PRACH preamble multiple times (for RXsweeping at the BS) using the determined UL TX beam and the calculatedTX power.

At operation 2509, the UE determines that RAR is successfully received.If received, at operation 2511, it is determined as a random accesssuccess. If not received, at operation 2513, the UE determines whetherPRACH is transmitted for all RX beams at the BS using the calculated TXpower. If the PRACH is not transmitted for all RX beams at the BS, goback for the operation 2507. If so, the UE determines whether the PRACHPreamble Transmission Counter is equal to MAX TX COUNTER at operation2515. If the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER, it is determined as a random access failure at operation 2517.If the PRACH Preamble Transmission Counter is not equal to MAX TXCOUNTER, the UE sets the Preamble Transmission Counter=PreambleTransmission Counter+1 at operation 2519, and then go back for theoperation 2503.

The MAX TX Counter can be predefined or can be configured by network(example by RRC signaling or in system information, and the like).

Method 3

This method of the disclosure is illustrated in FIGS. 26, 27, 28A, and28B according to an embodiment of the present disclosure.

FIG. 26 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIG. 26, the UE ramp up the power for PRACH preambleretransmission if TX beam is same as previous PRACH preambletransmission. The UE start from initial power for PRACH preambleretransmission, if TX beam is not same as previous PRACH preambletransmission. It is to be noted that during the PRACH preambletransmissions, if the UE repeats PRACH preamble transmission for RX beamsweeping at the BS, then the UE does not ramp up the power for thesetransmissions.

RA attempt is shown in FIG. 26. The UE first determines the UL TX beamfor PRACH preamble transmission. In an embodiment of the presentdisclosure, the UE measures the beamformed beam measurement signal (orSS or CSI-RS) transmitted by the BS and determines the best DL RX beami.e., the UE's RX beam with which it is able to receive the DL signalwith best quality. The UE uses the UL TX beam reciprocal (i.e., same orin same direction) to determined best DL RX beam. The UE transmits PRACHpreamble using UL TX beam one or more times using the power ‘P’ whereinthe UE may transmit multiple times for RX beam sweeping at the BS.

If the RAR is not received after transmitting PRACH preamble using power‘P’, the UE determines the UL TX beam for PRACH transmission again. Ifthe UL TX beam is not changed, the UE ramps up the power by Delta whereDelta is configured by the network and transmits using the same UL TXbeam one or more times using the power ‘P+Delta’ wherein these multipletransmissions are for RX beam sweeping at the BS. If the UL TX beam ischanged, the UE resets the power to an initial power and transmits usingthe changed UL TX beam one or more times using the initial power whereinthese multiple transmissions are for RX beam sweeping at the BS.

According to various examples, the UE can wait for the RAR aftertransmitting beam multiple times for RX beam sweeping partially. Forexample there are 10 RX beams at the BS, the UE transmits PRACH using TXbeam 5 times and then wait for the RAR. If the RAR is not received, theUE transmits beam for 5 more times.

FIG. 27 is a flowchart illustrating a method for power ramping during arandom access procedure in beamformed system according to an embodimentof the present disclosure.

Referring to FIG. 27, at operation 2701, the UE sets PRACH PreambleTransmission Counter to 1. At operation 2703, the UE determines the ULTX beam for PRACH preamble transmission.

At operation 2705, the UE sets TX power=P. P is an initial power whichcan be calculated based on DL received power as in prior art.

At operation 2707, the UE transmit PRACH preamble one or multiple times(for RX sweeping at the BS) using the determined UL TX beam and the TXpower.

At operation 2709, the UE determines that RAR is successfully received.If received, at operation 2711, it is determined as a random accesssuccess. If not received, at operation 2713, the UE determines whetherthe PRACH Preamble Transmission Counter is equal to MAX TX COUNTER. Ifthe Preamble Transmission Counter is equal to MAX TX COUNTER, it isdetermined as a random access failure at operation 2715. If the PRACHPreamble Transmission Counter is not equal to MAX TX COUNTER, the UEsets the PRACH Preamble Transmission Counter=Preamble TransmissionCounter+1 at operation 2717.

At operation 2719, the UE determines the UL TX beam for PRACHtransmission again. At operation 2721, the UE determines the UL TX beamis changed. If changed, go back to the operation 2705. If not changed,the UE sets the TX Power=TX Power+PowerRampingStep at operation 2723,and then go back for the operation 2707.

The MAX TX Counter can be pre-defined or can be configured by network(example by RRC signaling or in system information, and the like).

FIGS. 28A and 28B are flowcharts illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIGS. 28A and 28B, at operation 2801, the UE sets PRACHPreamble Transmission Counter to 1. At operation 2803, the UE determinesthe UL TX beam for PRACH preamble transmission.

At operation 2805, the UE sets TX power=P. P is an initial power whichcan be calculated based on DL received power as in prior art.

At operation 2807, the UE transmit PRACH preamble one or multiple times(for RX sweeping at the BS) using the determined UL TX beam and the TXpower.

At operation 2809, the UE determines that the RAR is successfullyreceived. If received, at operation 2811, it is determined as a randomaccess success. If not received, at operation 2813, the UE determineswhether PRACH is transmitted for all RX beams at the BS. If the PRACHpreamble is not transmitted for all RX beams at the BS, go back for theoperation 2805. If so, the UE determines whether the PRACH PreambleTransmission Counter is equal to MAX TX COUNTER at operation 2815. Ifthe PRACH Preamble Transmission Counter is equal to MAX TX COUNTER, itis determined as a random access failure at operation 2817. If the PRACHPreamble Transmission Counter is not equal to MAX TX COUNTER, the UEsets the PRACH Preamble Transmission Counter=PRACH seem PreambleTransmission Counter+1 at operation 2819.

At operation 2821, the UE determines the UL TX beam for PRACHtransmission again. At operation 2823, the UE determines the UL TX beamis changed. If changed, go back to the operation 2805. If not changed,the UE sets the TX Power=TX Power+PowerRampingStep at operation 2825,and then go back for the operation 2807.

The MAX TX Counter can be predefined or can be configured by network(example by RRC signaling or in system information, and the like).

Method 4

This method of the disclosure is illustrated in FIGS. 29, 30A and 30B,and 31A and 31B according to an embodiment of the present disclosure.

FIG. 29 is a schematic diagram illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIG. 29, the UE Ramp up the power for PRACH preambleretransmission if TX beam is same as previous PRACH preambletransmission. The UE uses the Power for PRACH preamble retransmissionsame as power of previous PRACH preamble transmission if TX beam is notsame as previous PRACH preamble transmission. It is to be noted thatduring the PRACH preamble transmissions, if the UE repeats PRACHpreamble transmission for RX beam sweeping at the BS, then the UE doesnot ramp up the power for these transmissions.

RA attempt is shown in FIG. 29. The UE first determines the UL TX beamfor PRACH preamble transmission. In an embodiment of the presentdisclosure, the UE measures the beamformed beam measurement signal (orSS or CSI-RS) transmitted by the BS and determines the best DL RX beami.e., the UE's RX beam with which it is able to receive the DL signalwith best quality. The UE uses the UL TX beam reciprocal (i.e., same orin same direction) to determined best DL RX beam. The UE transmits PRACHusing UL TX beam one or more times using the power ‘P’ wherein the UEmay transmit multiple times for RX beam sweeping at the BS.

If the RAR is not received, the UE determines the UL TX beam for PRACHpreamble transmission again. If the UL TX beam is not changed, the UEramps up the power by Delta where Delta is configured by network andtransmits using the same UL TX beam one or more times using the power‘P+Delta’. If the UL TX beam is changed, the UE sets the power toprevious power and transmits using the changed UL TX beam one or moretimes using the previous power.

According to various examples, the UE can wait for the RAR aftertransmitting beam multiple times for RX beam sweeping partially. Forexample there are 10 RX beams at the BS, the UE transmits PRACH using TXbeam 5 times and then wait for the RAR. If the RAR is not received, theUE transmits beam for 5 more times.

FIGS. 30A and 30B are flowcharts illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIGS. 30A and 30B, at operation 3001, the UE sets PRACHPreamble Transmission Counter to 1. At operation 3003, the UE determinesthe UL TX beam for PRACH preamble transmission.

At operation 3005, the UE sets TX power=P. P is an initial power whichcan be calculated based on DL received power as in prior art.

At operation 3007, the UE transmit PRACH preamble one or multiple times(for RX sweeping at the BS) using the determined UL TX beam and the TXpower.

At operation 3009, the UE determines that the RAR is successfullyreceived. If received, at operation 3011, it is determined as a randomaccess success. If not received, at operation 3013, the UE determineswhether the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER. If the PRACH Preamble Transmission Counter is equal to MAX TXCOUNTER, it is determined as a random access failure at operation 3015.If the PRACH Preamble Transmission Counter is not equal to MAX TXCOUNTER, the UE sets the PRACH Preamble Transmission Counter=PRACHPreamble Transmission Counter+1 at operation 3017.

At operation 3019, the UE determines the UL TX beam for PRACHtransmission again. At operation 3021, the UE determines the UL TX beamis changed. If changed, go back to the operation 3007. If not changed,the UE sets the TX Power=TX Power+PowerRampingStep at operation 3023,and then go back for the operation 3007.

The MAX TX Counter can be predefined or can be configured by network(example by RRC signaling or in system information, and the like).

FIGS. 31A and 31B are flowcharts illustrating a method for power rampingduring a random access procedure in beamformed system according to anembodiment of the present disclosure.

Referring to FIGS. 31A and 31B, at operation 3101, the UE sets PRACHPreamble Transmission Counter to 1. At operation 3103, the UE determinesthe UL TX beam for PRACH preamble transmission.

At operation 3105, the UE sets TX power=P. P is an initial power whichcan be calculated based on DL received power as in prior art.

At operation 3107, the UE transmit PRACH preamble one or multiple times(for RX sweeping at the BS) using the determined UL TX beam and the TXpower.

At operation 3109, the UE determines that the RAR is successfullyreceived. If received, at operation 3111, it is determined as a randomaccess success. If not received, at operation 3113, the UE determineswhether PRACH preamble is transmitted for all RX beams at the BS. If thePRACH prepare is not transmitted for all RX beams at the BS, go back forthe operation 3107. If so, the UE determines whether the PreambleTransmission Counter is equal to MAX TX COUNTER at operation 3115. Ifthe Preamble Transmission Counter is equal to MAX TX COUNTER, it isdetermined as a random access failure at operation 3117. If the PreambleTransmission Counter is not equal to MAX TX COUNTER, the UE sets thePreamble Transmission Counter=Preamble Transmission Counter+1 atoperation 3119.

At operation 3121, the UE determines the UL TX beam for PRACHtransmission again. At operation 3123, the UE determines the UL TX beamis changed. If changed, go back to the operation 3107. If not changed,the UE sets the TX Power=TX Power+PowerRampingStep at operation 3125,and then go back for the operation 3107.

The MAX TX Counter can be predefined or can be configured by network(example by RRC signaling or in system information, and the like).

According to various examples, Beam Gain and RACH Power Calculationduring Random Access in Beamformed System might be calculated based on:

Calculate path loss (PL_(c)) compensating for TX (at eNB) and RX (at UE)beamforming gain

P _(PRACH)=min{P _(CMAX,c)[i],PREAMBLE_RECEIVED_TARGET_POWER+PL _(c)},

where, P_(CMAX,c)[i], is the configured the UE transmits power forsubframe i of serving cell ‘c’

P _(CMAX_L,c) ≤P _(CMAX,c) <P _(CMAX_H,c)

P _(CMAX_H,c)=MIN{P _(EMAX,c) ,P _(PowerClass)}

P_(EMAX,c) is the value given by IE P-Max (in SIB1) for serving cell c

P_(PowerClass) is the maximum UE power

Scale P_(PRACH) considering TX/RX beamforming gain

In a plurality of the embodiment of the present disclosure, a RandomAccess procedure in NR (new radio access technology (RAT)) is provided.

Method 1

At higher frequency, beamforming is necessary to compensate for highpath loss. The UE/eNB needs to transmit/receive RA preamble and MSG3using beamforming. The ENB/UE needs to transmit/receive the RAR and MSG4using beamforming. The UE and eNB may support multiple TX/RX beams whereeach TX/RX beam covers a specific coverage area. If the beamforming issimply applied to each operation in RA procedure the resulting RAprocedure will look as shown in FIG. 32.

FIG. 32 is a flowchart illustrating a method for a random accessprocedure in a new radio access technology (RAT) according to anembodiment of the present disclosure.

Referring to FIG. 32, at operation 3210, the UE 3200 transmits RApreamble using all its TX beams, where each TX beam transmission isrepeated for each RX beam of the eNB 3205.

At operation 3215, the eNB 3205 transmits the RAR using all TX beams,where each TX beam transmission is repeated for each RX beam of the UE3200. The RAR includes TA, UL grant, RAPID (preamble index).

At operation 3220, the UE 3200 transmits MSG3 using all TX beams, whereMSG3 is transmitted once from each TX beam. The eNB 3205 receives MSG3using best UL RX beam where best UL RX beam is the RX beam which wasused to successfully receive RA preamble in operation 3210.

At operation 3225, the eNB 3205 transmits MSG4 using all TX beams, whereMSG4 is transmitted once from each TX beam. The UE 3200 receives MSG4using best DL RX beam where best DL RX beam is the RX beam which wasused to successfully receive the RAR in operation 3215.

Applying beamforming to each operation of RA procedure leads tosignificant:

Delay in completing the four steps of RA procedure because of TX/RX beamsweeping.

Wastage of resources as MSG3/MSG4 needs to be transmitted from each TXbeam of the UE and the eNB respectively.

Power consumption in the UE/eNB because of transmissions using multipleTX beams.

The above mentioned issues can be overcome if the number of TX/RX beamsused in each operation of RA procedure can be minimized (if possible,one TX/RX beam at each step).

Some of the potential enhancements to overcome the above mentionedissues are discussed below.

Method 2

This method of the disclosure is illustrated in FIG. 33 according to anembodiment of the present disclosure.

FIG. 33 is a flowchart illustrating a method for a random accessprocedure in the new RAT according to an embodiment of the presentdisclosure.

Referring to FIG. 33, in case of beamformed system, the eNB 3305 mayperiodically broadcast synchronization signals (e.g., primarysynchronization signal (PSS/secondary synchronization signal (SSS)) andbroadcast channel (e.g., physical broadcasting channel (PBCH)) usingbeamforming. The eNB 3305 may also periodically broadcast referencesignals using beamforming Before initiating the RA procedure, the UE3300 at least has to acquire these beamformed signals for DLsynchronization.

At operation 3310, the UE 3300 transmits RA preamble using all its TXbeams, where each TX beam transmission is repeated for each RX beam ofthe eNB 3305.

At operation 3315, the eNB 3305 transmits the RAR using all TX beams. Aspart of DL synchronization, the UE 3300 can know the best DL RX beam forreceiving the beamformed DL transmissions. The UE 3300 can receive theRAR using best DL RX beam instead of RX sweeping. The eNB 3305 does nothave to repeat the RAR transmission for each RX beam of the UE 3300. TheeNB 3305 transmits the RAR using all TX beams, where the RAR istransmitted once from each TX beam. The eNB 3305 inform the UE 3300about the time and frequency information of detected preamble in the RARin addition to RAPID.

At operation 3320, the UE uses the information received in the RAR todetermine the best UL TX beam. Best UL TX beam is the TX beam used bythe UE 3300 to transmit RA preamble identified by RAPID in the time andfrequency information received in the RAR. The UE 3300 can use best ULTX beam to transmit MSG3 instead of TX sweeping. At operation 3320, theUE 3300 transmits MSG3 using best UL TX beam Similar to determining thebest DL RX beam based on broadcasted beamformed DL signals (e.g.,PSS/SSS/PBCH/BRS), the UE 3300 can also determine the best DL TX beam.The UE 3300 can feedback the best DL TX beam ID or SS Block ID (SS blockID is the ID of SS block in which the UE has received thesynchronization signal or reference signal with best signal quality) tothe eNB 3305 in MSG3. As a result, the eNB 3305 does not have totransmit MSG4 using multiple TX beams. The eNB 3305 receives MSG3 usingbest UL RX beam where best UL RX beam is the RX beam which was used tosuccessfully receive RA preamble in operation 3310.

At operation 3325, the eNB 3305 transmits MSG4 using best DL TX beam(indicated by the UE in MSG3) and the UE 3300 receives MSG4 using bestDL RX beam. If SS block ID is reported by the UE 3300 instead of DL TXbeam ID, then the eNB 3305 transmits MSG4 using DL TX beam(s) totransmit synchronization signal or reference signal in the SS block ofthat SS block ID.

Method 3

This method of the disclosure is illustrated in FIG. 34 according to anembodiment of the present disclosure.

FIG. 34 is a flowchart illustrating a method for a random accessprocedure in the new RAT according to an embodiment of the presentdisclosure.

Referring to FIG. 34, in case of beamformed system, the eNB 3405 mayperiodically broadcast synchronization signals (e.g., PSS/SSS) andbroadcast channel (e.g., PBCH) using beamforming. The eNB 3405 may alsoperiodically broadcast reference signals using beamforming Beforeinitiating the RA procedure, the UE 3400 at least has to acquire thesebeamformed signals for DL synchronization.

At operation 3410, the UE 3400 transmits RA preamble using all its TXbeams, where each TX beam transmission is repeated for each RX beam ofthe eNB 3405. The UE 3400 feedbacks the best DL TX beam ID or SS blockID (SS block ID is the ID of SS block in which the UE has received thesynchronization signal or reference signal with best signal quality) atthis step. TX beam sweeping for the RAR transmission can be reduced ifbest DL TX beam ID or SS block ID is feed backed during RA preambletransmission instead of MSG3. In order to indicate DL TX beam ID or SSblock ID, this embodiment requires mapping between RA preamble(s) and DLTX beam ID/SS block ID and/or RA resource (time/frequency) and DL TXbeam ID/SS block ID.

At operation 3415, the eNB 3405 transmits the RAR using best DL TX beamindicated by the UE in operation 3410. If SS block ID is reported by theUE 3400 instead of DL TX beam ID, then the eNB 3405 transmits the RARusing DL TX beam(s) to transmit synchronization signal or referencesignal in the SS block of that SS block ID. The eNB 3405 informs the UE3400 about the time and frequency information of detected preamble inthe RAR in addition to RAPID. As part of DL synchronization the UE 3400can know the best DL RX beam for receiving the beamformed DLtransmissions. The UE 3400 can receive the RAR using best DL RX beaminstead of RX sweeping.

At operation 3420, the UE uses the information received in the RAR todetermine the best UL TX beam. Best UL TX beam is the TX beam used bythe UE 3400 to transmit RA preamble identified by RAPID in the time andfrequency information received in the RAR. The UE 3400 can use best ULTX beam to transmit MSG3 instead of TX sweeping. At operation 3420, theUE 3400 transmits MSG3 using best UL TX beam. MSG 3 may also includebest DL TX beam ID/SS block ID. The eNB 3405 receives MSG3 using best ULRX beam where best UL RX beam is the RX beam which was used tosuccessfully receive RA preamble in operation 3410.

At operation 3425, the eNB 3405 transmits MSG4 using best DL TX beam(indicated by the UE at operation 3410 or at operation 3420) and the UE3400 receives MSG4 using best DL RX beam.

Method 4

This method of the disclosure is illustrated in FIG. 35 according to anembodiment of the present disclosure.

FIG. 35 is a flowchart illustrating a method for a random accessprocedure in the new RAT according to an embodiment of the presentdisclosure.

Referring to FIG. 35, in case of time division duplex (TDD) system DLand UL channel can be reciprocal. Channel reciprocity can be used tosimplify the RA procedure in beamformed TDD system.

The UE 3500 can determine the best DL RX beam based on broadcastedbeamformed DL signals (e.g., PSS/SSS/PBCH/BRS). The UE 3500 then uses ULTX beam having same coverage as the best DL RX beam for transmission ofRA preamble and MSG3. At operation 3510, the UE 3500 can transmit RApreamble using UL TX beam once or multiple times (one for each RX beamof the eNB 3505). Network (eNB) 3505 may inform the UE 3500 usingbroadcast or dedicated signaling whether it needs to transmit RApreamble using TX beam once or multiple times (one for each RX beam ofthe eNB 3505). Network (eNB) 3505 may also inform the UE 3500 usingbroadcast or dedicated signaling whether it needs to transmit RApreamble using multiple TX beams. In alternate embodiment of the presentdisclosure, UL TX beam for MSG3 can also be determined using theprocedure explained in FIG. 33.

At operation 3515, the UE 3500 uses the best DL RX beam for reception ofthe RAR. The eNB 3505 transmits the RAR using the TX beam having samecoverage as the UL RX beam through which RA preamble was detected. TheRAR includes TA, UL grant, RAPID.

At operation 3520, the UE 3500 transmits MSG3 using best UL TX beam andthe eNB 3505 receives MSG3 using the UL RX beam through which RApreamble was detected.

At operation 3525, the eNB 3505 transmits MSG4 using best DL TX beam andthe UE 3500 receives MSG4 using best DL RX beam.

This approach is even better than RA procedure illustrated in FIG. 34 asthere is no TX beam sweeping for RA preamble transmission. Also there isno need of any beam feedback.

RACH transmission is different in operation of FIGS. 34 and 35. The UEneeds to know which operation to perform. In an embodiment of thepresent disclosure, network (eNB) can signal whether the UE performsRACH transmission as in FIG. 34 or 35. Alternately, the UE performs RACHtransmission as in FIG. 34 for an FDD system and as in FIG. 35 for a TDDsystem. Alternately, the UE performs operation as in FIG. 35 in the TDDsystem, if mapping between RA preamble(s) and DL TX beam ID or RAresource (time/frequency) and DL TX beam ID is not signaled by network.Alternately, the UE performs operation as in FIG. 35 if mapping betweenRA preamble(s) and DL TX beam ID or RA resource (time/frequency) and DLTX beam ID is not signaled by network.

In the operation of FIGS. 32, 33, 34, and 35, RACH resource is definedas a time-frequency resource to send RACH preamble. Network (eNB) mayinform (via broadcast or dedicated signaling) whether the UE needs totransmit one or multiple/repeated preamble within a subset of RACHresources. Network may inform the UE using broadcast or dedicatedsignaling whether it needs to transmit RA preamble using TX beam once ormultiple times (one for each RX beam of the eNB). Network may alsoinform the UE using broadcast or dedicated signaling whether it needs totransmit RA preamble using multiple TX beams. DL synchronisation signalsor reference signals or broadcast channel are transmitted multiple timesin case of beamforming system. One or multiple DL TX beams can be usedfor transmitting DL synchronisation signals or reference signals orbroadcast channel in each occasion. Network may indicate the associationbetween one or multiple occasions of DL broadcast signal/channel and asubset of RACH resources in broadcast or dedicated signaling. The UEselects the RACH resources for PRACH transmission (s) based onmeasurement of DL channel/signal and the association between occasionsof DL broadcast signal/channel and a subset of RACH resources. The UEselects the RACH resources corresponding to occasion in which it hasreceived the DL synchronisation signals or reference signals orbroadcast channel with best or suitable signal quality. In an embodimentof the present disclosure, the occasion can be an SS block.

According to various examples, the BS may inform the UE about theadditional reference signals to be measured by the UE in the RAR. Theseadditional reference signals may be transmitted using narrow beams.These narrow beams may be selected by the BS based on PRACH transmissionreceived from the UE.

The UE transmits the PRACH using PRACH resource corresponding to SSoccasion in which it has received the DL synchronisation signals orreference signals or broadcast channel with best or suitable signalquality. So, based on PRACH transmission the BS can know the occasion orSS block in which the UE has successfully received the DL signal. SSblock may be transmitted by the BS using wide beam or multiple narrowbeams. The additional reference signals indicated in the RAR correspondsto these narrow beams or narrow beams covering the area covered by widebeam.

After receiving the RAR, the UE perform the measurement of theseadditional reference signals and sends the report (e.g., one or morestrongest beams), in MSG3.

According to various examples, source the BS can provide the additionalreference signals of target BS to the UE in handover command. The UEperforms measurement of these additional reference signals and sends thereport (e.g., one or more strongest beams) to target the BS in MSG 3during the random access procedure with the target BS.

FIG. 36 is a block diagram of a terminal apparatus according to variousembodiments of the present disclosure.

Referring to FIG. 36, the terminal apparatus includes a transceiver 3600(ex) RF module, and the like) and a controller 3605 (ex) at least oneprocessor). The transceiver 3600 is capable of transmission/reception ofsignals to/from at least one base station (ex) MeNB, SeNB) bycontrolling of the controller. The controller 3605 is capable ofperforming operations of terminal (UE) in the various embodiments of thepresent disclosure.

FIG. 37 is a block diagram of a base station (ex) MeNB or SeNB)according to various embodiments of the present disclosure.

Referring to FIG. 37, the base station includes a transceiver 3700 (ex)RF module, and the like) and a controller 3705 (ex) at least oneprocessor). The transceiver 3700 is capable of transmission/reception ofsignals to/from at least one terminal and another base station bycontrolling of the controller. The controller 3705 is capable ofperforming operations of a base station (MeNB or SeNB) in the variousembodiments of the present disclosure.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: selecting a firstsynchronization signal block (SSB) based on a measurement of at leastone SSBs; transmitting, to a base station, a first physical randomaccess channel (PRACH) preamble in a first PRACH occasion correspondingto the first SSB, using a first transmission beam based on a firstpower; identifying that a random access response is not received fromthe base station as a response to the PRACH preamble; selecting a secondSSB based on a measurement of at least one SSBs; identifying a secondpower for transmitting a second PRACH preamble based on a counterassociated with preamble transmission power ramping; and transmitting,to the base station, the second PRACH preamble in a second PRACHoccasion corresponding to the second SSB, using a second transmissionbeam based on a second power, wherein the counter associated withpreamble transmission power ramping is not incremented for identifyingthe second power in case that the second transmission beam is differentfrom the first transmission beam.
 2. The method of claim 1, wherein thecounter associated with preamble transmission power ramping isincremented for identifying the second power in case that the secondtransmission beam is same as the first transmission beam.
 3. The methodof claim 1, wherein the first SSB is selected based on signal strengthof the first SSB being above a threshold.
 4. The method of claim 1,wherein the second SSB is selected based on signal strength of thesecond SSB being above a threshold.
 5. The method of claim 1, furthercomprising: receiving, from the base station, configuration informationby a broadcast signaling or a dedicated signaling, the configurationinformation including information on PRACH occasions and information onassociation between the PRACH occasions and SSBs.
 6. The method of claim5, wherein the first PRACH occasion corresponding to the first SSB isidentified based on the configuration information, and the second PRACHoccasion corresponding to the second SSB is identified based on theconfiguration information.
 7. The method of claim 1, wherein differentSSBs correspond to different beams.
 8. A terminal in a wirelesscommunication system, the terminal comprising: a transceiver; and atleast one processor configured to: select a first synchronization signalblock (SSB) based on a measurement of at least one SSBs, transmit, to abase station via the transceiver, a first physical random access channel(PRACH) preamble in a first PRACH occasion corresponding to the firstSSB, using a first transmission beam based on a first power, identifythat a random access response is not received from the base station as aresponse to the PRACH preamble, select a second SSB based on ameasurement of at least one SSBs, identify a second power fortransmitting a second PRACH preamble based on a counter associated withpreamble transmission power ramping, and transmit, to the base stationvia the transceiver, the second PRACH preamble in a second PRACHoccasion corresponding to the second SSB, using a second transmissionbeam based on a second power, wherein the counter associated withpreamble transmission power ramping is not incremented for identifyingthe second power in case that the second transmission beam is differentfrom the first transmission beam.
 9. The terminal of claim 8, whereinthe counter associated with preamble transmission power ramping isincremented for identifying the second power in case that the secondtransmission beam is same as the first transmission beam.
 10. Theterminal of claim 8, wherein the first SSB is selected based on signalstrength of the first SSB being above a threshold.
 11. The terminal ofclaim 8, wherein the second SSB is selected based on signal strength ofthe second SSB being above a threshold.
 12. The terminal of claim 8,wherein the at least one processor is further configured to receive,from the base station via the transceiver, configuration information bya broadcast signaling or a dedicated signaling, the configurationinformation including information on PRACH occasions and information onassociation between the PRACH occasions and SSBs.
 13. The terminal ofclaim 12, wherein the first PRACH occasion corresponding to the firstSSB is identified based on the configuration information, and the secondPRACH occasion corresponding to the second SSB is identified based onthe configuration information.
 14. The terminal of claim 8, whereindifferent SSBs correspond to different beams.